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Translated from the Second German Edition by M. M. Pattison Muir, with Notes and Additions. Illustrated. Crown 8vo. 7s. 6d. PRACTICAL CHEMISTRY FOR MEDICAL STUDENTS. By M. M. Pattison Muir, F.R.S.E. Fcap. 8vo. 1s. 6d. A COURSE OF PRACTICAL INSTRUCTION IN ELEMENTARY BIOLOGY. By T. H. Huxley, LL.D., Sec. R.S., assisted by H. N. Martin, B.A., M.B., D.Sc., Fellow of Christ’s College, Cambridge. Crown 8vo. 6s. MACMILLAN & CO., LONDON. Footnotes 1.This expression is found for the first time, it would appear, in Theophrastus, B.C. 371. [See, however, Herodotus, Bk. II., chap. 77. Speaking of some Egyptians he says, “They drink a kind of wine made from barley (???? d’ ?? ??????? pep??????), for the grape does not grow in that part of the country.” Herodotus wrote about 450 B.C. Æschylus (480 B.C.) has a similar expression, Suppl. 953.—D. C. R.] 2.One of these modifications is a real source of serious danger to the preservation of wine; for instance, during rainy years, at the time of vintage, the grapes may happen to be covered with earthy matter, consisting principally of carbonate of lime; this will dissolve in wine and partly neutralize its acidity, and the wine will thus become more liable to disease. 3.Transferring from one cask to another for the purpose of clarifying the wine. 4. We shall hereafter revert to this rapidity in cooling, to show that it is also of use in the subsequent clarification of beer. 5.In some breweries (at Lyons especially) fermentation at a high temperature is practised in large vats at about 15° C. (59° F.). The yeast which covers the surface of the liquid is skimmed off and stored in flat tubs. 6.The initial temperature of the wort must be regulated by the quantity of wort subjected to fermentation. In English breweries, where large quantities are brewed at a time, the heat created by the action of fermentation would produce a temperature sufficiently high to affect the quality of the beer, if the yeast were added at 19° C. or 20° C. The following are the temperatures at which the worts are pitched, in the principal London breweries:—For common ale, 60° F. or 15·5° C.; for pale ale, 58° F. or 14·4° C.; for porter, 64° F. or 17·8° C. The fermentation is commenced in large vats; from these the beer is run into vessels of a much smaller capacity, in which it completes its fermentation by working off the yeast and cleansing itself. For white beer of superior quality, the temperature during fermentation must not rise beyond 72° F. or 22·2° C.; some brewers never allow it to exceed 18°C. (65° F.). The temperature is lowered by means of a current of cold water, which circulates through a coil fixed in the vats or other fermenting vessels. In the case of porter, the initial heat of which is 64° F. or 17·8° C., the temperature in the vats sometimes rises to 78° F. or 25·5° C.; but such an increase in temperature excites considerable apprehension. We have seen a tun for pale ale, containing 200 barrels of 36 gallons, pitched with 600 lbs. of fairly solid yeast. In forty-six hours the attenuation was considered sufficient, and the beer, which from an initial heat of 58·1° F. or 14·5° C., had risen to 72° F. or 22·2° C., was cleansed to working casks. The large vats in which the fermentation is started may be considered as equivalent to the cuves guilloires of French breweries, the casks in which it is completed and the yeast thrown off representing their 75-litre vessels, improperly called quarts. Notwithstanding the enormous English beer manufacture, and although the fermenting vat, as in making porter, for instance, sometimes attains the capacity of 2,000 to 3,000 litres (400 to 600 gallons), the casks into which it is run are never larger than 15 to 20 hectolitres (300 to 400 gallons); and even at Burton, in the celebrated breweries of Allsopp and Bass, the pale ale is finished in casks of a capacity less than 10 hectolitres, and yet the average turn-out of these immense works reaches 3,000 to 4,000 hectolitres (60,000 to 80,000 gallons) of beer per day. 7.[The expressions “high” and “low” fermentation or beer strictly refer to temperature, whereas the other expressions used (“top” or “bottom”) refer to the behaviour of the yeast. The French words haute and basse seem to look both ways.—D. C. R.] 8.It is said that the floating cones or cylinders filled with ice, which enable brewers to manufacture beer at a low temperature, even in summer, were first used in Alsace. 9.45 million kilos. of ice are annually consumed in the brewery of M. Dreher, in Vienna. The brewery of Sedlmayer, at Munich, uses about 10 million kilos. (Journal des Brasseurs, 22nd June, 1873.) 10.It should, however, be borne in mind that these remarks on the relative preservative powers of the two beers hold true on account of three things—differences in the respective modes of brewing, artificial cooling during the process of fermentation, and the storing of the “low beer” in ice-cellars. In itself, perhaps, “low beer” is more liable to change than “high beer;” that this does not actually take place, is due to the employment of artificial cooling. A brewery which has an average annual production of 10,000 hect. will use 8,000 cwt. of ice. If we add to this the ice used during the retail of the beer, which is best drunk at 12° C. (54° F.), we shall arrive at the total of 100 kilos. per hectolitre. 11.[In connection with the comparison here instituted by M. Pasteur between the drinking and keeping qualities of the two kinds of beer, it may be useful to draw the reader’s attention to a review by Dr. Charles Graham of the French edition of this work, published in Nature for January 11th, 1877, page 216. At the same time we must remark that Dr. Graham appears to have overlooked M. Pasteur’s footnote, page 12, English edition:—“His assertion, that by bottom fermentation store beers can be produced, whereas those produced by top fermentation must be consumed at once and cannot be transported, are certainly strange to an Englishman. So far from these unfavourable comparisons being true in all cases, the exact opposite is generally the case. Bavarian and other bottom fermentation beers are in fact those which can neither be preserved nor transported without the liberal employment of ice; even that sent from Vienna to London must be kept cold artificially, in order to avoid rapid destruction. As regards flavour, there are many who think a glass of Burton pale ale, or of good old College rent ale, to be superior to any Bavarian beer. The chief cause of the decline in the production of top fermentation beers on the Continent has been the want of attention in the fermentation process; whereas the English brewer, especially the brewer of high-class ales, has been unremitting in his attention to the temperature in fermentation and to the perfect cleansing of the ale. Now, where such attention is given, it is not difficult to obtain ales which will keep a few years. While objecting to our English produce being so hastily depreciated by M. Pasteur, our brewers will be the first to avail themselves of his biological researches, in order to render their produce more stable and better flavoured, without having recourse to the general adoption of the vastly more costly system of bottom fermentation.”—D. C. R.] 12.To preserve bottled beer from deterioration, some bottlers employ, at the moment of filling, a small quantity of bisulphite of lime. Others heat the bottles to a temperature of 55° C. (131° F.) In the north of Germany and in Bavaria, this practice has been widely adopted since the publication of the author’s “Studies on Wine,” and some of M. Velten’s writings. The process has been termed pasteurization in recognition of the author’s discovery of the causes of deterioration in fermented liquors, and of the means of preserving such liquors by the application of heat. Unfortunately this process is less successful in the case of beer than in that of wine, for the delicacy of flavour which distinguishes beer is affected by heat, especially when the beer has been manufactured by the ordinary process. This effect would be less felt in beer manufactured by the process which is advocated in this work. 13.A convincing proof of the influence of hops on the ferment organisms is contained in the fact that beer, even after being raised to 60° C. or 70° C. (140° or 160° F.), will, if unhopped, readily take on the butyric fermentation, from which, if hopped, it would remain perfectly free. 14.For historical details, see l’EncyclopÉdie, Art. BiÈre. 15.As a wine-producing country France has been highly favoured by nature, but the consumption of beer in France is increasing every year. In 1873 the quantity of beer, paying excise duties, amounted to 7,413,190 hect., which yielded to the Treasury the sum of 20,165,136 fr. These figures are taken from a report published in 1875 by M. JacquÈme, inspector of finances, who remarks that the quantity of beer upon which excise duties are paid represents, probably, not more than one-third of the total production: two-thirds of the quantity brewed evades the duties. 16.A statement of this proposition, as far as it concerns beer, appeared first in outline in the author’s Etudes sur le vin, published in 1866. 17.As the deposit in the heated bottles is, as a rule, inconsiderable, it is necessary to exercise some precaution in collecting it. The bottles are taken up; after some days’ rest they are decanted very carefully, with as little shaking as possible, until not more than one or two cubic centimetres (about a tea-spoonful) of the liquid remains at the bottom. The bottles are then shaken vigorously, with the object of collecting the whole of the deposit from the bottom and the sides into this small quantity of liquid; a drop of this is then examined under the microscope. 18.Since the publication of the author’s “Studies on the Diseases of Wine, and the Dangers resulting to Wine and Beer from the Microscopic Parasites found therein,” some intelligent brewers have derived considerable profit from the application of the theories laid down in that work. 19.If we put a handful of germinating barley from a maltster’s cistern into a little water, and examine drops of the liquid, after it has become turbid, under a microscope, we shall be amazed at the wonderful number of strange microscopic organisms that swarm on the surface of the grains and on the sides of the cistern. There is no doubt that their presence is injurious to germination, inasmuch as they absorb much oxygen; moreover, they acidify the grain and cause it to deteriorate. 20.In these experiments the asbestos is only introduced by way of extra precaution. Originally, in his early experiments in connection with the subject of spontaneous generation, the results of which were published in 1860-62, the author did not use it, and he observed no ill effects resulting from the omission; now, however, he constantly makes use of it. In studies of this kind novel precautions are never thrown away; moreover, the presence of this asbestos is a sure bar to the entrance of insects. The author has preserved for a long time a flask, in the slender neck of which an insect is contained; he killed it with a flame just as it was approaching the liquid. Quite recently, M. Calmettes, a young engineer from the École Centrale, when engaged, at Tantonville, in Tourtel’s brewery, in carrying out certain practical experiments in connection with the process that will he described in one of the later chapters of this work, wrote complaining that his flasks had been suddenly invaded by a swarm of aphides, scarcely larger than phylloxeras, and that many of them had even penetrated into the inside of the curved tubes. 21.We have heard of liquids even less sensitive than these, which required a temperature of 120° C. (248° F.) or more, but we have had no opportunity of studying them. 22.See Pasteur, MÉmoire sur les GÉnÉrations dites SpontanÉes (Annales de Chimie et de Physique, t. lxiv. 3e sÉrie, annÉe 1862). 23.See my MÉmoire sur les GÉnÉrations dites SpontanÉes, already cited. 24.Jules Duval (of Versailles), Nouveaux faits concernant la mutabilitÉ des germes microscopiques. RÔle passif des Êtres classÉs sous le nom de ferments. (See the Journal d’Anatomie et de Physiologie, edited by C. Robin, Sept. and Oct. 1874, and Compte-rendus de l’AcadÉmie des Sciences, Nov. 1874). M. BÉchamps had previously fallen into similar errors. 25.On this subject see the observations of M. Coste (Compte-rendus de l’AcadÉmie, t. lix. pp. 149 and 358, 1864). 26.Chauveau’s experiments were directed to show that the operation bistournage, employed by veterinary surgeons for castrating animals by twisting and subcutaneous rupture of the spermatic cord, an operation which, though leading to the mortification and subsequent absorption of the testicles, is commonly attended with no other mischief to the animal, does, nevertheless, lead to septic effects of a serious character, provided that septic germs—decomposing serum containing vibrios, for example—be introduced into the blood current. From the fact that the operation is ordinarily harmless, M. Chauveau concludes that septic organisms are not produced by the action of the constituent gases of the atmosphere—always present in the blood—upon albuminous matter when outside vital influences; whilst, from the success of the direct experiment of introducing septic germs, he concludes that the phenomena always arise from the actual presence of such germs.—D. C. R. 27.See Pasteur, MÉmoire sur les GÉnÉrations dites SpontanÉes, pp. 51 and 52, 1862. 28.Davainne, Compte-rendus de l’AcadÉmie des Sciences, t. lvii. p. 220, 1863. Coze and Feltz, Recherches cliniques et expÉrimentales sur les maladies infectieuses, Paris, J. B. BailliÈre, 1872. Summary of all their works published before 1865. Dr. Lister, Medical and surgical journals, particularly the Lancet, 1865-67. Dr. GuÉrin, Compte-rendus de l’AcadÉmie des Sciences, March 23, 1874, and May 28, 1874, also the Report of M. Gosselin, December, 1854. Dr. SÉdillot, Compte-rendus de l’AcadÉmie des Sciences, November, 1874, t. lxxix. p. 1108. Pasteur, MÉmoire sur la fermentation appelÉe lactique. (Annales de Chimie et de Physique, t. lii. 3e sÉrie, 1875.)—Animalcules infusoires, vivant sans gaz oxygÈne libre et dÉterminant des fermentations. (Compte-rendus de l’AcadÉmie des Sciences, t. lii. 1861.)—Recherches sur la putrÉfaction. (Compte-rendus de l’AcadÉmie des Sciences, t. lvi. 1863.) Gosselin, Robin, and Pasteur, Compte-rendus de l’AcadÉmie des Sciences, January 5, 1874. Urines ammoniacales. Traube, Gazette hebdomadaire de mÉdecine et de chirurgie. Sur la fermentation alcaline de l’urine, April 8, 1864. Chauveau, PutrÉfaction dans l’animal vivant. (Compte-rendus de l’AcadÉmie des Sciences, April 28th, 1873.) 29.We must mention one curious result, which relates to what have been called the crystals of the blood. We could hardly have recourse to a better method of preparing these crystals, at least in the case of dog’s blood, which seems to yield them with the greatest facility in any quantity we might desire to procure. Under the circumstances just recounted, in which dog’s blood exposed to contact with pure air underwent no putrefactive change whatever, the crystals of that blood formed with a remarkable rapidity. From the first day that it was placed in the oven and exposed to an ordinary temperature, the serum began gradually to assume a dark brown hue. In proportion as this effect was produced, the globules of blood disappeared, and the serum and the coagulum became filled with very distinct crystals, of a brown or red colour. In the course of a few weeks, not a single globule of blood remained, either in the serum or coagulum; every drop of serum contained thousands of these crystals, and the smallest particle of coagulum, when bruised under a piece of glass, presented to view colourless and very elastic fibrine, associated with masses of crystals, without the slightest trace of blood-globules. Where our observations were protracted, it sometimes happened that all the fibrine collected into one hyaline mass, which gradually expelled every crystal from its interior. 30.Pasteur, Comptes rendus de l’AcadÉmie des Sciences, t. lvi. p. 738, 1863. 31.Gayon, Comptes rendus de l’AcadÉmie des Sciences, and Annales Scientifiques de l’École Normale SupÉrieure, 1874-75. 32.Amongst these influences one of the most important, according to M. Fremy, is “organic impulse,”—another gratuitous assumption. 33.Fremy, Comptes rendus de l’AcadÉmie des Sciences, t. lviii. p. 1167, 1864. 34.Fremy, Comptes rendus de l’AcadÉmie des Sciences, t. lxxiii. p. 1425, 1871. M. TrÉcul shares M. Fremy’s opinions, and extends them to the development of different fungoid growths. 35.This observation had already been made by Anthon and H. Hoffmann. “If we scrape the surface of a gooseberry with a blunt knife,” says H. Hoffmann, “and put under the microscope the scrapings, which are of a whitish colour, we shall recognize amongst many varieties of shapeless dirt, earthy particles and other things, the same fungoid spores that we find in the expressed juice, but we shall see them there in infinitely larger quantities. Some of them will be of a dusky colour (Stemphylium, Cladosporium), and others will be colourless; the shape of these latter will be round or oval, and cylindrical. Most of them will bear resemblance to beads of the chaplets of Oidium, Monilia, Torula (that is to say, to spores of certain Hyphomycetes), which have been detached and carried off by the wind, and have attached themselves to the fruit. Some of these spores will be already provided with short germinating filaments.” (Annales des Sciences Naturelles, Botanique, t. xiii. p. 21, 1860). 36.The experiments that we have described give rise to a useful remark. All the organic liquids, boiled or not, in the course of time must take up oxygen from the air. At the same time, and certainly under this influence, they assume an amber or brownish colour, but this effect is only produced when the liquids are placed under conditions of unalterability. Should fermentation or the development of fungoid growths be possible, scarcely any change of colour will take place. Doubtless this non-coloration may be attributed to the fact that these organisms consume the oxygen necessary for coloration. In these experiments on must, all the unchanged flasks assumed a pale yellowish brown colour; those which fermented or contained fungoid growths remained colourless, or nearly so. 37.Comptes rendus de l’AcadÉmie, sÉance du 28 Octobre, 1872. 38.Gay-Lussac, Annales de Chimie, t. lxxvi. p. 245; read at the Institute, December 3rd, 1810. Long before Gay-Lussac, it had been remarked that atmospheric air had a great influence on fermentation. See M. Chevreul’s articles on the history of chemistry in the Journal des Savants. 39.Gay-Lussac, Annales de Chimie, t. lxxvi. p. 247, MÉmoire citÉ, 1810. 40.It is well to notice that under the influence of fungoid growths, properly so called, the wort of beer speedily becomes bright. We may say that fungoid growths, by their rapid development, clarify the must, which serves to nourish them. 41.It has already been observed in our Memoir on spontaneous generation, that alcoholic fermentation is not always to be obtained by sowing wads of cotton or asbestos, charged with the particles of dust which float through the air, in saccharine musts that are in contact with much air. The air which furnished the particles of dust, in the experiments to which we are alluding, was taken outside the laboratory, in a neighbouring street. 42.The decanting into the flasks is necessary, because of the possibility of the fermentation in the basins being masked. See further on the note on p. 75. 43.This small ferment is very curious, although it scarcely affects industrial fermentation. It was first described in 1862. (Pasteur, Bulletin de la SociÉtÉ chimique, 1862, page 67, and following: Quelques faits nouveaux au sujet des levÛres alcooliques.) It has since been described by Dr. Rees under the name Saccharomyces apiculatus. (Dr. Rees, Leipzig, 1870: Sur les champignons de fermentation alcooliques. See also Dr. Engel, ThÈse pour le Doctorat, Paris, 1872.) If we carefully filter some grape must at the time of vintage, we may be sure that we shall see it appear in the clear liquid at the bottom of our vessel, without intermixture with any other ferment. Should we not filter the must this ferment will appear all the same, but it will soon become associated with another, thicker in appearance and more elongated, which also is one of the ferments peculiar to the fermentation of grape must. 44.We may remind the reader that in 1862, in our MÉmoire sur les GÉnÉrations dites spontanÉes, we applied the expression of torula to all the little cellular plants of spontaneous growth, excepting mycelium, propagated by budding, after the manner of the ferment of beer. At the same time, stress was laid upon the frequent occurrence of their germs, especially in our laboratory, where studies on fermentation were, even then, carried on. Plate III. represents two of these ferments. 45.It is to be remarked that in this case, as in the case recorded § IV. p. 70, in order to detect with certainty any alcoholic ferment, the contents of the basins were transferred to a long-necked flask; since where, as in the basins, a liquid has a large surface exposed to spontaneous impregnation, the strictly alcoholic fermentation may escape observation. The reason of this is that, when a liquid of large surface but small depth is exposed to the air it affords a suitable medium for the active development of moulds, which, by absorbing the oxygen which would dissolve in the liquid, checks the growth of the ferment, or even prevents its germination altogether. As a matter of fact we shall see that for their growth and multiplication ferment cells, and still more ferment germs (the difference between the two will appear in Chap. V.), require a larger supply of oxygen just in proportion to their age, state of desiccation, and distance from the budding condition. Now, if the spores of moulds be present and effect a settlement in the liquid, the increase of the ferment, or even its actual germination, is prevented. But by collecting the liquid in a deep and narrow vessel, such as a long-necked flask, after it has been exposed to spontaneous impregnation, we deprive the moulds almost completely of oxygen, and so allow the ferment to exert its peculiar energies. The mere act of transferring enables the liquid to take up a sufficiency of oxygen, and a liberation of gas very speedily shows that fermentative action is going on. We must add further that sometimes in a liquid of large surface and shallow depth, in which but little ferment is formed, the evolution of carbonic acid gas may fail to be detected, by reason of its diffusing itself into the air slowly as it is formed. 46.Here we had to seek for a most minute quantity of alcohol, that no alcoholometer could have indicated. A certain sign of the presence of alcohol is contained in the first few drops distilled; these always assume the form of little drops or striÆ or, better still, oily tears, when alcohol is present in the distillate. The distillation should be effected with a small long-necked retort and a Liebig’s condenser. We must carefully watch the neck of the retort at the moment of boiling; should the liquid contain 1/1000 part of its volume of alcohol, we shall observe the indications given above for a short, but appreciable time. 1/10,000 of alcohol is difficult to judge, but with care and practice we may do it without failing. Collecting a third of each distillate, and supposing the limit of appreciation to stop at thousandths, in three distillations we may easily detect the presence of 1/10,000 of 1 c.c. of alcohol in a total volume of 100 c.c. 47.Yeast when macerated in water imparts to it certain soluble nitrogenous materials. The solution so obtained, filtered from yeast globules, is known as yeast water.—D. C. R. 48.It is possible that this greasiness in the cells of the common mycoderma vini arises simply from the composition of the liquid in which it vegetates. It is in saccharine liquids that the submerged torulÆ are found; fermented liquids more readily give birth to the forms of torulÆ and mycoderma vini which exist as a scum. In all probability, however, there is no radical difference between these two kinds of little cellular plants of aerial growth, the floating torulÆ and mycoderma vini. 49.In the course of this work we shall combat, by means of experimental proofs which appear to us irrefragable, the opinions which many writers entertain on the subject of certain transformations of organisms—that of penicillium glaucum into ferment, or mycoderma; of bacteria into lactic ferment; of ferment into vibrios; of mycoderma aceti into ferment, and so on. Nevertheless, we shall pronounce no a priori opinion on the question whether the inferior organisms, which will be the subject of this chapter, and which include yeast and the ferments properly so called, are perfect beings in their habitual form, or whether they are susceptible of polymorphism. It is with this reservation that we employ the word autonomy. If we claim polymorphism for any species, we shall not do so without furnishing proofs. Some organs detached from higher organisms, and some beings in a certain phase of their existence, may reproduce themselves under a special form, with special properties, when brought into media and under conditions that are unfit for the production of the plant or animal under its other shape or ordinary mode of reproduction. Modern Science affords many examples of this, and certain alcoholic ferments present us with analogous facts; but to wish to stretch these facts beyond their due significance, and to admit a polymorphism that cannot be proved, in consequence of a belief that it is possible, or on the faith of confused observations, is to indulge in gratuitous assertion from a mere spirit of system. 50.See, on this subject, the author’s Études sur le Vinaigre, Paris, 1868, p. 76, note; and especially Études sur le Vin, 2nd Edition, 1873, p. 19. 51.Some observations in the preceding chapter enable us to account for the vast number of germs which are constantly falling on the surface of everything. We may here allude to the use we have made of flasks, shaped as in Fig. 17, and holding from 250 c.c. to 300 c.c., which are a third part filled with an organic liquid, and are closed up when boiling. They contain no air when cool, and are opened in series of 10, 20, &c., out of doors, and closed up again immediately. The air rushes violently into the vacuum, and thus we introduce about 200 c.c. of air, with all the particles of dust contained in that air, into each flask. It has been proved that a certain number of these flasks undergo change in the course of time, the number of those changing and the nature of their changes being in close proportion to the probable number and nature of the floating germs able to develop in the particular nutritive liquid used. If we work at great elevations, far from houses and the dirt of towns and inhabited plains, as we did at Montanvert, near the Mer de Glace, change will seldom occur. The opposite will be the case if we work in a place like the living-room of the little, dirty, ill-kept inn at Montanvert. In a laboratory where fermentation is studied we obtain certain kinds of germs which often differ from those found in the air of the open country. If we desire to have organisms in all our flasks, we have only to stir up the dust on the ground or on surrounding objects at the moment when we open the flasks. This simple and easy experiment clearly shows us that it is impossible for a field of sporanges of fungoid growth, existing in an uncovered vessel or on the surface of a fruit, to escape becoming mixed with germs that are foreign to the little plant; in other words, the student who sows spores of penicillium, which he has collected from one place or another on a brush, exposes himself to serious causes of error. 52.M. Jules Raulin has published a well-known and remarkable work on the discovery of the mineral medium best adapted by its composition to the life of certain ordinary fungoid growths; he has given a formula for the composition of such a medium. It is this that we call here “Raulin’s fluid” for abbreviation.
J. Raulin. Paris, Victor Masson, 1870. ThÈse pour le doctorat. 53.If we do not wish to take the chance of procuring the pure penicillium by means of these spontaneous sowings, effected by opening and then closing in the flame a certain number of flasks with drawn-out points, we may utilize one of the flasks, which, having been opened and closed again, has notwithstanding developed no organized forms, as follows:—We impregnate the contained liquid directly, by dropping into it from a metallic wire spores taken from any growth of penicillium exposed to the common air; and then from the new field of sporanges formed by this sowing in the flask that has been re-closed, we must, later on, take the pure spores that we require. This method is quicker and almost as safe. We should add that, if we wish to use for our purpose spores of penicillium from a closed flask, in which the plant has fructified, we must be careful not to leave the plant too long closed up. A few days after the sowing the growth of the fungus is arrested, in consequence of all the oxygen being absorbed, and its place being supplied by a mixture of carbonic acid and nitrogen; and the spores, if kept too long in this atmosphere, will all perish. 54.To shake the liquid without danger of introducing exterior particles of dust, we apply the flame of the spirit lamp to the drawn-out neck of the flask, and close up the open end; we may then shake our flask without risk. We must afterwards reopen the end of the drawn-out neck for the purpose of re-establishing communication with the exterior air. 55.The flask B was closed with the lamp in consequence of one of the objects of these experiments being to test M. TrÉcul’s experiments on the transformation of penicillium into ferment. Strangely enough, according to M. TrÉcul, as we shall see later on, the spores of penicillium refuse to change into ferment, if the vessels in which they are sown are not “perfectly air-tight.” 56.Bulletin de la SociÉtÉ Philomathique. 57.Hermann Hoffmann, Études Mycologiques sur la Fermentation. Botanische Zeitung and Annales des Sciences Naturelles, 4e sÉrie, t. xiii. p. 24, 1860. 58.Communication sur l’Origine et le DÉveloppement de quelques Champignons. Dantzig, 1867. 59.TrÉcul, Comptes rendus de l’AcadÉmie, t. lxxiii. p. 1454; December 28, 1871. 60.TrÉcul, Comptes rendus de l’AcadÉmie, t. lxxv. p. 1169, November 11, 1872. A proof of M. TrÉcul’s carelessness in experiments of this kind is the fact that in studying the fertility of an impregnated wort, he often obtains different productions. Our experiments give opposite results. If we sow nothing, we obtain nothing. If we sow a plant, we obtain a similar plant; or, should there be any difference, the change may be traced, beyond question, to its origin in the plant sown, and is the consequence of some alteration in the conditions of our experiment. 61.Comptes rendus des SÉances de l’AcadÉmie des Sciences, t. lxxv. p. 1220; Nov. 18, 1872. 62.Since writing the above we have experienced some doubt as to whether the forms of development represented in Fig. 20 are actually those of the aspergillus glaucus, which we supposed our fungoid growth to be. In some of the later sketches of our observations we find similar forms, which belong to a bluish kind of penicillium, with rather large spores. Fortunately, this doubt affects our argument in no essential particular. It matters very little what variety of fungoid growth it is that gives rise to alcoholic fermentation attended by peculiarities of shape that only occur in the development of its spores when air fails it. 63.By the term conidia is meant certain chains of cells, which are in reality mycelial spores. 64.See Pasteur, Études sur le Vin, 1st Edition, pp. 20 and following. 65.Since writing this paragraph, we have found in M. Ch. Robin’s Journal d’Anatomie et de Physiologie, an article signed by that gentleman, and entitled Sur la Nature des Fermentations, &c. (July-August, 1875), in which the learned microscopist says:—“The torula cerevisiÆ is derived from the mycoderma cerevisiÆ. My observations leave no doubt on my mind that penicillium glaucum is one of the forms evolved from spores or ferments that have preceded it, as M. TrÉcul showed a long time ago, and that, moreover, the spores of penicillium, germinating in suitable media, give us the sporical form termed mycoderma.” We take the liberty to observe that these assertions of M. Robin’s are purely gratuitous. Up to the present time it has been impossible to discover a suitable medium for the proof of these different transformations or polymorphisms. From the time of Turpin, who firmly believed that he had observed these changes, to our own, none of the microscopists who have affirmed these transformations have succeeded in adducing any convincing proof of them, and M. TrÉcul’s latest observations, especially as regards penicillium and its transformation into ferment or into the mycoderma of beer, have been positively disproved by ours, supported, as they are, by proofs that we consider irrefutable. 66.It is a very easy matter to study the liquids and growths in our flasks during the course of a single experiment. We take out the glass stopper that closes the india-rubber tube on the straight-neck, and, by means of a long rod or a glass tube previously passed through the flame, take up a quantity, which we draw out immediately for microscopical examination. We then replace the glass stopper, taking care to pass it through the flame before doing so, to burn up any organic particles of dust that it may have picked up from the table on which we laid it. 67.We may prove the occurrence of alcoholic fermentation by the cells of submerged mycoderma vini in a different manner. To do this, after having made all our preparations as before and shaken up the film of mycoderma vini in its liquid, we must attach our flask to a test flask (Fig. 19), and pass the turbid liquid into the latter. On succeeding days we shall detect a very protracted fermentation in the test flask; there will be a succession of minute bubbles rising from the bottom, but in small number at a time. The fermentation is very evident whilst it lasts, but is rather sluggish, and, although of very long duration, ceases long before the sugar is exhausted. This experiment proves better than any other the non-transformation of mycoderma vini into other ordinary fungoid growths. For after decanting the liquid into the test flasks, the sides of the experimental flask remain covered with streaks of mycoderma vini along with some of the liquid. Moreover, the flask is refilled with air, and this air is being constantly renewed, in part, by variations of the temperature of the oven, so that the mycoderma remaining on the sides is thus placed under the most favourable conditions for transformation into other fungoid growths, if that were possible. It is still more easy to detach the experimental from the test flask, and to pass pure air into it, once or twice a day, or constantly. In any case, we shall never see anything besides the mycoderma vini spring up within it. 68.See Pasteur, Comptes rendus des SÉances de l’AcadÉmie des Sciences, t. liv., 1862, and t. lv., 1862. Études sur les Mycodermes, &c. 69.In a subsequent chapter we shall prove that yeast is likewise incapable of transformation into mycoderma vini. 70.We secured the purity of our mycoderma by the same means that we have already described for the procuring of spores of penicillium or other fungoid growths in a state of purity. 71.Buffon, Histoire de l’Homme, t. viii., edition 12mo, 1778; Turpin, MÉmoires de l’AcadÉmie des Sciences, t. xvii.; Dr. Pineau, Annales des Sciences Naturelles, t. iii., 1845; Pouchet, TraitÉ de la GÉnÉration dite SpontanÉe, p. 335, 1859. See also our MÉmoire sur les GÉnÉrations dites SpontanÉes, 1862, pp. 100 and following, in which we give a resumÉ of some of these theories. 72.The following is Turpin’s application of his theory to the formation of the ferments of fruits (MÉmoires de l’AcadÉmie, t. xvii., 1840, p. 155), where also, on p. 171 the above quotation will be found:—Ferments Produced by the Filtered Juice of the Pulp of Different Fruits—“By the word pulp we mean the soft and juicy cellular tissue of the fleshy part, mesocarp or middle layer of the pericarp of certain ripe fruits. This cellular tissue, which is very abundant in the peach and all stone-fruit, in the apple and pear, in the orange and grape, and similar fruits, is the same as that which forms the body of a leaf. Being in every case composed of a simple agglomeration of contiguous mother-vesicles, which are always filled with globulines that are more or less developed, more or less coloured, and individually endowed with a special vital centre, it is not surprising that its globulines when free and detached from the compound organisms to which they belong, and from association with its vegetable life, should, when placed in a suitable medium, themselves vegetate and become transformed, under these new influences, into a mucedine, with filaments and articulations. Such are the very fine, and, consequently, very transparent globulines, which, when left to themselves in sweetened water, grow and become vesicular, producing other globulines in their interior, then bud, vegetate into mucedinous filaments, decompose sugar, and produce all the effects that constitute what we term alcoholic fermentation.” 73.BÉchamp, Recherches sur la Nature et l’Origine des Ferments (Annales de Chimie et de Physique, 4e sÉrie, t. xxiii., and Comptes rendus de l’AcadÉmie des Sciences, Oct. 23, 1871). 74.We need scarcely here observe, having done so on previous occasions, that whenever we opened our flasks to obtain specimens, we made use of a fine tube, previously passed through the flame of a spirit lamp, and that we also passed this flame over the surface of the india-rubber, glass stopper, &c., to consume the organic particles of dust which floating about might introduce themselves at the moment when we opened the right-hand tube of the flask. 75.Ever since the year 1861 (see p. 92), this question of the possible transformation of the ordinary fungi, especially penicillium and mucor mucedo, into yeast has engaged our attention. The results attained have been entirely negative; but hitherto only the conclusions of our work have been published, some account of which was given at the meeting of the SociÉtÉ Philomathique of March 30th, 1861. The following extract is from the Bulletin of the society:—“Meeting of March 30th, 1861. At this meeting a paper was read by M. Pasteur ‘On the supposed changes in the form and vegetation of yeast-cells, depending on the external condition of their development.’ It is well-known that Leuwenhoeck was the first to describe the globules of yeast, and that M. Cagnard-Latour discovered their faculty of multiplying by budding. This interesting vegetable organism has been the subject of a host of researches by chemists and botanists. The latter, from the days of Turpin and Kutzing, have almost unanimously regarded yeast as a form of development of various inferior vegetable types, especially penicillium. The studies of this subject which seem to have won most favour during the last few years are those of MM. Wagner, Bail, Berkeley, and H. Hoffmann. The researches of these botanists seem to strengthen and confirm the original observations of Turpin and Kutzing. M. Pouchet has, quite recently, expressed the same ideas, and has determined certain points in connection with them with much precision of detail. M. Pasteur has long studied this important question, which is so intimately connected with the essential nature of yeast and with those phenomena of the polymorphism of the inferior types of vegetable life, to which most of the remarkable works of M. Tulasne relate; he has, however, arrived at results that are altogether negative, and he declares that he was unable to detect the transformation of yeast into any of the mucedines whatsoever, and, inversely, that he could never succeed in producing the smallest quantity of yeast from ordinary mucedines.” These same results we communicated to the SociÉtÉ Chimique of Paris, at a meeting held April 12th, 1861. Throughout the investigation of which we have just indicated the conclusions, we insisted on the necessity of cultivating the separate organisms in a state of purity in all researches relating to these inferior forms of life, if we desire to attain to sure inferences about them; and the method of working, which we recommended, did not differ essentially from that adopted in the present work. Since then the study of these growths has been conducted with the utmost precautions; and other apparatus, perhaps as safe as those which we employ and better adapted than ours for the study of polymorphism of species, have been invented by botanists of great skill—M. de Bary, in Germany, and M. Van Tieghem, in France. 76.We found, after the lapse of another year, in December, 1873, that the ferment of the mucor in the test glass might still be easily revived; that it was able to propagate, both in the mycelium and in the cellular form, in wort, and that it might produce a fermentation, more or less active, according to the condition of aeration; in short, that it was capable of producing all the characteristic phenomena described. By means of the method of cultivation that we employ, our study, which was continued for years, was pursued without the least fear of any foreign fungoid growths being introduced into the vessels, although they remained constantly open, and the air in them was being perpetually renewed by the action of diffusion and variations of temperature. In 1875 nothing remained alive in our flask, and further revival became impossible. 77.We do not here take into account certain phenomena of oxidation of which the fungoid growths are the seat, and which remind us of those that are presented in so remarkable a degree by mycoderma vini and mycoderma aceti. 78.[There are 15·43 grains in the gramme.] 80.The figure given below supplies this omission. The cells that are isolated or are in chains, b.b.b., show this state of the old cells. The cells a.a.a. are younger, and may be more easily revived. We may see by the dimensions of some of these how greatly, in certain cases, the cells of mucor resemble cells of yeast; nevertheless, in the state of the contents and the aspect of the outlines, there are always some differences sufficiently appreciable to strike the practised observer. Fig. 23. Fig. 23. The figures adjoining the cells indicate fractions of a millimetre. (A millimetre may be taken as ½5-in.) 81.[0·000089 in., 0·00026 in. and O·00089 in. respectively.] 82.Extract from a Note which I inserted in 1862 in the Bulletin de la SociÉtÉ chimique of Paris. 83.SchÜtzenberger, in his work on “Fermentation,” following Dr. de VaurÉal. Paris, 1875, p. 278. [See pp. 61, 62 English version in International Scientific Series (H. S. King & Co., London, 1876). This appears to be the only reference to this subject in the English copy.—D. C. R.] 84.The principal result of Dr. Rees’ labours consists in the discovery of a sporulation peculiar to yeast cells, that is to say, to a formation in the interior of these cells, and under particular conditions—such as when the growth occurs on slices of cooked potatoes, carrots, &c.—of two, three, or four smaller cells, which, when placed in fermentable liquids, act like the germinating spores of ferments. The mother-cell may be regarded as an ascus, and the daughter-cells as ascospores, and so the genus saccharomyces may be classified among the group of fungi termed ascomycetes. These facts have been frequently confirmed, notably by Dr. Engel, professor of the Faculty of Medicine, at Nancy. Previously to Dr. Rees’ discovery, M. de Seynes (Comptes rendus, t. lxvii., 1868) had described an endogenous formation of spores in mycoderma vini, particularly in the elongated cells, followed by the rupture of the mother-cell, and subsequent absorption of cell-walls and other contents after the issue of the endospores, which we have just termed ascospores. We ourselves had also previously called attention to those refractive corpuscles which appear amongst vibrios as probably being reproductive corpuscles, and we had likewise witnessed the reabsorption of the parts surrounding them. The plate on page 228 of our “Studies on the Silkworm Disease” represents the phenomena in question. 85.See Comptes rendus de l’AcadÉmie des Sciences, vol. lviii. p. 144. 86.The plates referred to in this paragraph were exhibited at a meeting of the Academy of Sciences, November 18, 1872, and commented upon by the perpetual secretary, M. Dumas. 87.For these observations, we employed small glass cells, which we made out of some St. Gobain glass by punching holes through it, and then cementing on one side one of the little glasses used for covering objects in microscopical examinations. In this manner we made small troughs, in which we placed some wort that had been boiled, and a drop of the water in which grapes had been washed. To prevent evaporation we covered the cells with a sheet of glass. We examined the liquid in these cells by inclining our microscope to the angle required. Fig. 29. Fig. 29. We also made use of cells similar to those employed by MM. Van Tieghem and Lemonnier Fig. 30. Fig. 30. An apparatus similar to that employed by M. Duclaux in 1853 Fig. 31. Fig. 31. 88.In our essay on acetic fermentation, published in 1864, we have already described this apparatus, which we employed to follow the multiplication of the jointed filaments of mycoderma aceti. See Pasteur, Etudes sur le vinaigre, p. 64, Paris, 1868. 89.Van Tieghem and Lemonnier, Annales des Sciences naturelles, 5th series, Botanique, t. xvii. 1873. 90.Duclaux, Comptes rendus des sÉances de l’AcadÉmie des Sciences, t. lvi. p. 1225. 91.In experiments of this kind there is always a slight increase in the volume of air in the jar. This increase may be very perceptible even when the experiment made with fresh grapes, in August, for instance, causes no fermentation due to the action of yeast. After the oxygen of the air has been absorbed and replaced by carbonic acid gas, either by direct oxidation or by the action of moulds, the grapes, although crushed, act like fruits plunged into carbonic acid gas 92.See paragraph: Fermentation in saccharine fruits immersed in carbonic acid gas, Chap. vi, § 2, p. 266. 93.Dr. Rees has given the name saccharomyces ellipsoideus to the ferment of wine represented in Plates VIII. to XI. of our “Studies on Wine,” which we have termed the ordinary ferment of wine, from its being the most abundant of the ferments found at the end of the fermentation that produces the wine. 94.The alcoholic ferments in general, subjected to these weakening influences, have not all the same power of resistance. That one which seems to possess this power in the highest degree is the saccharomyces pastorianus, which ferment we had in view in writing the above. 95.The term exhaustion (Épuisement), which we have just used, was, perhaps, not altogether felicitously chosen. No doubt we exhaust the cells of yeast when we sow an imponderable weight of them in a large quantity of sweetened water; it might, however, be better to say that in such a case we adopt a particular method of preserving the vitality of the cells, without suffering them to die of exhaustion, or to multiply by budding. We may remark that the yeast, in this case, exists in a state of latent life, which resembles that of cells on the surface of fruit. The cells on the surface of fruits, bunches, or barks, can no more find around them sufficient aliment for their propagation than can our yeast-cells in a great excess of sweetened water. We would not, however, say of the spores on the surface of fruits, or their woods, that they are in a state of exhaustion; the term would be misapplied. 97.M. BÉchamp (Comptes rendus, November 18th, 1872) asserts that the air has no direct influence on the production of ferment or on the process of alcoholic fermentation. That experienced chemist deduces this erroneous assertion from experiments on sweetened water, to which bunches of grapes, petals of corn-poppies and petals of robinia pseudo-acacia had been added. As may be seen in our “Studies on Wine” (p. 7, 1st edition, 1866), these experiments conducted by M. BÉchamp in 1872 were merely a reproduction of those made long before with vine leaves, petals of elder-flowers, leaves of sorrel, &c., by the Marquis de Bullion, Fabroni, and other experimentalists. M. BÉchamp has modified his later experiments by not adding the bunches of grapes, leaves, &c., to the sweetened water before having introduced carbonic acid gas into the liquid. Fermentation having still taken place in spite of this change, M. BÉchamp wrongly concluded that air has no direct influence on the production of yeast on an alcoholic fermentation. The introduction of the carbonic acid gas could not remove all the air imparted to the sweetened water by the objects placed in it, and it was this air which remained adhering to these objects that permitted the production of fermentation. We may avail ourselves of the opportunity here presented to add that, in this same Note of November, 1872, M. BÉchamp commences by making various assertions concerning the forms assumed by cells of the alcoholic ferment of the grape when in process of fermentation. This question was discussed by us ten years before, and our conclusions supported by sketches, in a Note which appeared in the Bulletin de la SociÉtÉ chimique de Paris, for 1862. 98.The germs of ferments are less widely diffused than M. de Bary supposes, as may be seen from our observations in Chap. III. See, too, our Memoir of 1862, Sur les GÉnÉrations dites SpontanÉes, p. 49. It is only in a laboratory devoted to researches on fermentation, or places such as vaults, cellars, and breweries, that the air holds appreciably in suspension cells of ferments, ready to germinate in saccharine media. If we except these particular circumstances, ferment is not very largely diffused, save on the surface of fruits and the wood of the trees which bear them, and perhaps, also, on some other plants. The particles of dust held in suspension in any atmosphere whatever rarely produce fermentation in pure must even when we take all possible precautions, so that the action be not overlooked; for true fermentation may be hidden by fungoid growths, when there is much air and but a small quantity of saccharine liquid present. 99.In these experiments the apiculated ferment appeared sometimes, but much less frequently than saccharomyces pastorianus. We also met with the ellipsoidal ferment. We should probably have a greater variety of ferments if our experiments could be conducted in the open air, but insects and particles of dust of all kinds brought by the wind render experiments under such conditions difficult and untrustworthy. In a laboratory we have not these difficulties to contend against, but, unfortunately, the operations ordinarily carried on there cause the results of our experiments to be of a less general character than they would be if obtained in free contact with country air. 100.[A rather serious clerical error appears to have here crept into the original, for on referring to Plate I. and the letterpress descriptive of No. 7 (p. 5), we find it applies to a very formidable species of diseased ferment, whereas the author is here speaking of an amorphous deposit, harmless in character, and more or less associated with all yeasts. Doubtless No. 7 should stand No. 6, see p. 6.—D. C. R.] 101.[We would here call the reader’s attention to the following extract from Dr. Graham’s appreciative review of this work in “Nature,” January 11th, 1877. He says: “M. Pasteur seems to be in error in stating (p. 190, Fr. ed.) that the bottom yeast may be distinguished by being less spherical than top yeast. It is true that in London and Edinburgh yeast, the cells will be found usually round; hard water, however, such as that at Burton, or artificially made so, yields yeast in which the cells are distinctly ovoid in appearance, resembling very closely Bavarian bottom yeast.”—D. C. R.] 102.[43° F. to 46° F. or 59° F. to 68° F.] 103.[On this point again Dr. Graham expresses some dissent (“Nature,” loc. cit.): “Here surely M. Pasteur must be thinking rather of the inferior products of the surface fermentation in France and Germany, than of those of England and Scotland.”—D. C. R.] 104.[28·4 c.c. = 1 fl. oz. approximately.] 105.[M. Pasteur has evidently employed the word “caseous” to express the curdy nature of the ferment he is describing, its plasticity and other peculiarities of physical character; but we are, nevertheless, tempted to suggest that he may have had in mind also the peculiar “cheesy” odour given off by these very yeasts, which he refers to in the text as containing a considerable intermixture of “caseous ferment.”—F. F.] 106.The caseous ferment, however, must not be exposed to heat, under the afore-mentioned conditions, when it is too young. At the commencement of its development, for instance, within a few days of having been sown. In such case, it would be in danger of perishing, probably in consequence of the tenderness of its tissues. At the end of a fermentation, and even several months afterwards, it might be safely heated to 50° C. (122° Fahr.) without any harm to it. “Low” yeast also can withstand a temperature of 50° C. in the medium in question. 107.Although we believe that the aËrobian ferment of a particular yeast may be produced by a kind of transformation of the cells of the latter, yet we admit that this question is open to some doubt. The facts which we unexpectedly discovered in connection with the caseous ferment should make us extremely careful, and disposed to inquire whether aËrobian ferments do not originally, in a state of intermixture, form part of the ferments from which they spring. One reason which might incline us to believe this, is the fact that a ferment sometimes perishes without the appearance of aËrobian ferment on the surface. There is nothing very natural indeed in the hypothesis that we advance, which sets aside the supposed intermixture; but, on the other hand, if the aËrobian ferment is a particular ferment, simply intermixed with some other variety and developed by change of conditions, how are we to account for its great resemblance in appearance and mode of budding to the ferment on the surface of which it appears? This resemblance, however, might be accounted for very naturally if the two ferments were originally related. 108.We insist on this fact, that Fig. 50 represents the forms on revival of the aËrobian ferment of saccharomyces pastorianus, when this has grown in a mineral medium. When produced on the surface of fermented wort, the aËrobian ferment of which we are speaking presents no peculiarity, nor is there any irregularity in its forms or in its development, and when we proceed to cultivate it in a natural saccharine medium, or in wort, it does not produce any forms of dematium, as in the preceding case; but the reason of this is that, in consequence of the nature of the first medium, which is better adapted to its nutrition, it assumes at once, in the second medium, the forms of deposit-yeast in the course of ordinary germination. 109.“La cassure de la levÛre.” 110.We have reason to believe that the ratio of the proportions of these ferments depends greatly on the climatic conditions preceding the period of vintage, on the state of dryness or humidity, as well as the temperature at the time of gathering the grapes, and also on the nature of the vines. 111.It has been remarked in practice that fermentation is facilitated by leaving the grapes on the bunches. The reason of this has not yet been discovered. Still we have no doubt that it may be attributed, principally, to the fact that the interstices between the grapes, and the spaces which the bunch leaves throughout, considerably increase the volume of air placed at the service of the germs of ferment. 113.[This appears to be a misprint for 1·638 grammes = 25·3 grains.—D.C.R.] 114.[200 c.c. of liquid were used, which, as containing 5 per cent., had in solution 10 grammes of sugar.—D. C. R.] 115.[International Science Series, vol. xx., pp. 179-182. London, 1876.—D. C. R.] 116.Page 182, English edition. 117.This figure is on a scale of 300 diameters, most of the figures in this work being of 400 diameters. 118.[It may be useful for the non-scientific reader to put it thus:—that the 25 c.c. which escaped, being a fair sample of the whole gas in the flask, and containing (1) 25 - 20·6 = 4·4 c.c., absorbed by potash and therefore due to carbonic acid, and (2) 20·6 - 17·3 = 3·3 c.c., absorbed by pyrogallate, and therefore due to oxygen, and the remaining 17·3 c.c. being nitrogen, the whole gas in the flask, which has a capacity of 315 c.c., will contain oxygen in the above proportion, and therefore its amount may be determined, provided we know the total gas in the flask before opening. On the other hand, we know that air normally contains, approximately, 1/5th its volume of oxygen, the rest being nitrogen, so that, by ascertaining the diminution of the proportion in the flask, we can find how many cubic centimetres have been absorbed by the yeast. The author, however, has not given all the data necessary for accurate calculation.—D.C.R.] 119.This number is probably too small; it is scarcely possible that the increase of weight in the yeast, even under the exceptional conditions of the experiment described, was not to some extent at least due to oxidation apart from free oxygen, inasmuch as some of the cells were covered by others. The increased weight of the yeast is always due to the action of two distinct modes of vital energy—activity, namely, in presence and activity in absence of air. We might endeavour to shorten the duration of the experiment still further, in which case we would still more assimilate the life of the yeast to that of ordinary moulds. 120.In these experiments, in which the moulds remain for a long time in contact with a saccharine wort out of contact with oxygen—the oxygen being promptly absorbed by the vital action of the plant (see our MÉmoire sur les GÉnÉrations dites SpontanÉes, p. 54, note)—there is no doubt that an appreciable quantity of alcohol is formed because the plant does not immediately lose its vital activity, after the absorption of oxygen. A 300-c.c. (10-oz.) flask, containing 100 c.c. of must, after the air in it had been expelled by boiling, was opened and immediately re-closed, on August 15th, 1873. A fungoid growth—a unique one, of greenish-grey colour—developed from spontaneous impregnation, and decolorized the liquid, which originally was of a yellowish-brown. Some large crystals, sparkling like diamonds, of neutral tartrate of lime, were precipitated. About a year afterwards, long after the death of the plant, we examined this liquid. It contained 0·3 gramme (4·6 grains) of alcohol, and 0·053 gramme (0·8 grain) of vegetable matter, dried at 100° C. (212° F.). We ascertained that the spores of the fungus were dead at the moment when the flask was opened. When sown, they did not develop in the least degree. 121.We find in M. Raulin’s Note, already quoted, that “the minimum ratio between the weight of sugar and the weight of organized matter, that is, the weight of fungoid growth which it helps to form, may be expressed 10/3·2 = 3·1.” Jules Raulin, Études chimiques sur la vÉgÉtation. Recherches sur le dÉveloppement d’une mucÉdinÉe dans un milieu artificiel, p. 192, Paris, 1870. We have seen, in the case of yeast, that this ratio may be as low as 4/1. 122.We shall show, some day, that the processes of oxidation due to growth of fungi cause, in certain decompositions, liberation of ammonia to a considerable extent, and that by regulating their action we might cause them to extract the nitrogen from a host of organic dÉbris, as also, by checking the production of such organisms, we might considerably increase the proportion of nitrates in the artificial nitrogenous substances. By cultivating various moulds on the surface of damp bread in a current of air, we have obtained an abundance of ammonia, derived from the decomposition of the albuminoids effected by the fungoid life. The decomposition of asparagus, and several other animal or vegetable substances, has given similar results. 123.To determine the absence of cells of ferment in fruits that have been immersed in carbonic acid gas, we must first of all carefully raise the pellicle of the fruit, taking care that the subjacent parenchyma does not touch the surface of the pellicle, since the organized corpuscles existing on the exterior of the fruit might introduce an error into our microscopical observations. Experiments on grapes have given us an explanation of a fact generally known, the cause of which, however, had hitherto escaped our knowledge. We all know that the taste and aroma of the vintage, that is, of the grapes stripped from the bunches and thrown into tubs, where they get soaked in the juice that issues from wounded specimens, are very different from the taste and aroma of an uninjured bunch. Now grapes that have been immersed in an atmosphere of carbonic acid gas have exactly the flavour and smell of the vintage; the reason is that, in the vintage tub, the grapes are immediately surrounded by an atmosphere of carbonic acid gas, and undergo, in consequence, the fermentation peculiar to grapes that have been plunged in this gas. These facts deserve to be studied from a practical point of view. It would be interesting, for example, to learn what difference there would be in the quality of two wines, the grapes of which, in the one case, had been perfectly crushed, so as to cause as great a separation of the cells of the parenchyma as possible; in the other case, left, for the most part, whole, as in the case in the ordinary vintage. The first wine would be deprived of those fixed and fragrant principles produced by the fermentation of which we have just spoken, when the grapes are immersed in carbonic acid gas. By such a comparison as that which we suggest, we should be able to form an À priori judgment on the merits of the new system, which has not been carefully studied, although already widely adopted, of milled, cylindrical crushers, for pressing the vintage. 124.We have sometimes found small quantities of alcohol in fruits and other vegetable organs, surrounded with ordinary air, but always in small proportion, and in a manner which suggested its accidental character. It is easy to understand how, in the thickness of certain fruits, certain parts of those fruits might be deprived of air, under which circumstance they would have been acting under conditions similar to those under which fruits act when wholly immersed in carbonic acid gas. Moreover it would be useful to determine whether alcohol is not a normal product of vegetation. 125.In these studies on plants living immersed in carbonic acid gas, we have come across a fact which corroborates those which we have already given in reference to the facility with which lactic and viscous ferments, and, generally speaking, those which we have termed the disease-ferments of beer, develop when deprived of air, and which shows, consequently, how very marked their aËrobian character is. If we immerse beetroots or turnips in carbonic acid gas, we produce well-defined fermentations in those roots. Their whole surface readily permits the escape of the highly acid liquids, and they become filled with lactic, viscous, and other ferments. This shows us the great danger which may result from the use of pits, in which the beetroots are preserved, when the air is not renewed, and that the original oxygen is expelled by the vital processes of fungi, or other deoxidizing chemical actions. We have directed the attention of the manufacturers of beetroot sugar to this point. 126.Lechartier and Bellamy, Comptes rendus de l’AcadÉmie des Sciences, vol. lxix., pp. 366 and 466, 1869. 127.Those gentlemen express themselves thus: “In a note presented to the Academy in November, 1872, we published certain experiments which showed that carbonic acid and alcohol may be produced in fruits kept in a closed vessel, out of contact with atmospheric oxygen, without our being able to discover alcoholic ferment in the interior of those fruits. “M. Pasteur, as a logical deduction from the principles which he has established in connection with the theory of fermentation, considers that the formation of alcohol may be attributed to the fact that the physical and chemical processes of life in the cells of fruit continue under new conditions, in a manner similar to those of the cells of ferment. Experiments, continued during 1872, 1873, and 1874, on different fruits, have furnished results all of which seem to us to harmonize with this proposition, and to establish it on a firm basis of proof.” Comptes rendus, t. lxxix., p. 949, 1874. 128.Pasteur, Faites nouveaux pour servir À la connaissance de la thÉorie des fermentations proprement dites. (Comptes rendus de l’AcadÉmie des Sciences, t. lxxv., p. 784). See, in the same volume, the discussion that followed; also, Pasteur, Note sur la production de l’alcool par les fruits, same volume, p. 1054, in which we recount the observations anterior to our own, made by Messrs. Lechartier and Bellamy in 1869. 129.Comptes rendus, meeting of January 15th, 1872. 130.As a matter of fact, M. Fremy applies his theory of hemi-organism, not only to the alcoholic fermentation of grape juice, but to all other fermentations. The following passage occurs in one of his Notes (Comptes rendus de l’AcadÉmie, t. lxxv., p. 979, October 28th, 1872): “Experiments on Germinated Barley.—The object of these was to show that, when barley, left to itself in sweetened water, produces in succession alcoholic, lactic, butyric, and acetic fermentations, these modifications are brought about by ferments which are produced inside the grains themselves, and not by atmospheric germs. More than forty different experiments were devoted to this part of my work.” Need we add that this assertion is based on no substantial foundation? The cells belonging to the grains of barley, or their albuminous contents, never do produce cells of alcoholic ferment, or of lactic ferment, or butyric vibrios. Whenever those ferments appear they may be traced to germs of those organisms, diffused throughout the interior of the grains, or adhering to their exterior surface, or existing in the water employed, or on the sides of the vessels used. There are many ways of demonstrating this, of which the following is one: since the results of our experiments have shown that sweetened water, phosphates, and chalk very readily give rise to lactic and butyric fermentations, what reason is there for supposing that if we substitute grains of barley for chalk, the lactic and butyric ferments will spring from those grains, in consequence of a transformation of their cells or albuminous substances? Surely, there is no ground for maintaining that they are produced by hemi-organism, since a medium composed of sugar, or chalk, or phosphates of ammonia, potash, or magnesia contains no albuminous substances. This is an indirect but irresistible argument against the hemi-organism theory. 131.Pasteur, MÉmoire sur la fermentation alcoolique, 1860; Annales de Chimie et de Physique. The word globules is here used for cells. In our researches we have always endeavoured to prevent any confusion of ideas. We stated at the beginning of our Memoir of 1860, that: “We apply the term alcoholic to that fermentation which sugar undergoes under the influence of the ferment known as beer yeast.” This is the fermentation which produces wine and all alcoholic beverages. This, too, is regarded as the type for a host of similar phenomena, designated, by general usage, under the generic name of fermentation, and qualified by the name of one of the essential products of the special phenomenon under observation. Bearing in mind this fact in reference to the nomenclature that we have adopted, it will be seen that the expression alcoholic fermentation cannot be applied to every phenomenon of fermentation in which alcohol is produced, inasmuch as there may be a number of phenomena having this character in common. If we had not at starting defined that particular one amongst the number of very distinct phenomena, which, to the exclusion of the others, should bear the name alcoholic fermentation, we should inevitably have given rise to a confusion of language that would soon pass from words to ideas, and tend to introduce unnecessary complexity into researches which are already, in themselves, sufficiently complex to necessitate the adoption of scrupulous care to prevent their becoming still more involved. It seems to us that any further doubt as to the meaning of the words alcoholic fermentation, and the sense in which they are employed, is impossible, inasmuch as Lavoisier, Gay-Lussac, and ThÉnard have applied this term to the fermentation of sugar by means of beer yeast. It would be both dangerous and unprofitable to discard the example set by those illustrious masters, to whom we are indebted for our earliest knowledge of this subject. 132.See, for example, the communications of MM. Colin and Poggiale, and the discussion on them, in the Bulletin de l’AcadÉmie de MÉdicine, March 2nd, 9th, and 30th, and February 16th and 23rd, 1875. 133.We have elsewhere determined the formation of minute quantities of volatile acids in alcoholic fermentation. M. BÉchamp, who studied these, recognized several belonging to the series of fatty acids, acetic acid, butyric acid, &c. “The presence of succinic acid is not accidental, but constant; if we put aside volatile acids that form in quantities which we may call infinitely small, we may say that succinic acid is the only normal acid of alcoholic fermentation.” Pasteur, Comptes rendus de l’AcadÉmie, t. xlvii. p. 224, 1858. 134.Traube’s conceptions were governed by a theory of fermentation entirely his own, a hypothetical one, as he admits, of which the following is a brief summary: “We have no reason to doubt,” Traube says, “that the protoplasm of vegetable cells is itself, or contains within it, a chemical ferment which causes the alcoholic fermentation of sugar; its efficacy seems closely connected with the presence of the cell, inasmuch as, up to the present time, we have discovered no means of isolating it from the cells with success. In the presence of air, this ferment oxidizes sugar, by bringing oxygen to bear upon it; in the absence of air it decomposes the sugar by taking away oxygen from one group of atoms of the molecule of sugar and bringing it to act upon other atoms; on the one hand yielding a product of alcohol by reduction, on the other hand a product of carbonic acid by oxidation.” Traube supposes that this chemical ferment exists in yeast and in all sweet fruits, but only when the cells are intact, for he has proved for himself that thoroughly crushed fruits give rise to no fermentation whatever in carbonic acid gas. In this respect this imaginary chemical ferment would differ entirely from those which we call soluble ferments, since diastase, emulsine, &c., may be easily isolated. For a full account of the views of Brefeld and Traube, and the discussion which they carried on on the subject of the results of our experiments, our readers may consult the Journal of the Chemical Society of Berlin, vii. p. 872. The numbers for September and December, 1874, in the same volume, contain the replies of the two authors. 135.See Pasteur, Comptes rendus de l’AcadÉmie des Sciences, t. lvi. p. 416. 136.[Carbonic acid being considerably more soluble than other gases possible under the circumstances.—Ed.] 137.We had to avoid filling the small flask completely, for fear of causing some of the liquid to pass on to the surface of the mercury in the measuring tube. The liquid condensed by boiling forms pure water, the solvent affinity of which for carbonic acid, at the temperature we employ, is well known. 138.The following is a curious consequence of these numbers and of the nature of the products of this fermentation. The carbonic acid liberated being quite pure, especially when the liquid has been boiled to expel all air from the flask, and capable of perfect solution, it follows that, the volume of liquid being sufficient and the weight of tartrate suitably chosen—we may set aside tartrate of lime in an insoluble, crystalline powder, along with phosphates at the bottom of a closed vessel full of water, and find soon afterwards in their place carbonate of lime, and, in the liquid, soluble salts of lime, with a mass of organic matter at the bottom, without any liberation of gas or appearance of fermentation ever taking place, except as far as the vital action and transformation in the tartrate are concerned. It is easy to calculate that a vessel or flask of five litres (rather more than a gallon) would be large enough for the accomplishment of this remarkable and singularly quiet transformation, in the case of fifty grammes (767 grains) of tartrate of lime. 139.We treated the whole deposit with dilute hydrochloric acid, which dissolved the carbonate of lime, and the insoluble phosphates of calcium and magnesium; afterwards filtering the liquid through a weighed filter paper. Dried at 100° C. (212° F.), the weight of organic matter thus obtained was 0·54 gramme (8·3 grains), which was rather more than 1/200th of the weight of fermentable matter. 140.Should the solution of lactate of lime be turbid, it may be clarified by filtration, after previously adding a small quantity of phosphate of ammonia, which throws down phosphate of lime. It is only after this process of clarification and filtration that the phosphates of the formula are added. The solution soon becomes turbid, if left in contact with air, in consequence of the spontaneous formation of bacteria. 141.The naturalist Cohn, of Breslau, who published an excellent work on bacteria in 1872, described, after Mayer, the composition of a liquid peculiarly adapted to the propagation of these organisms, which it would be well to compare for its utility in studies of this kind with our solution of lactate and phosphates. The following is Cohn’s formula:—
This liquid, the author says, has a feeble acid reaction and forms a perfectly clear solution. 142.On the rapid absorption of oxygen by bacteria, see also our MÉmoire of 1872, sur les GÉnÉrations dites SpontanÉes, especially the note on page 78. 143.In what way are we to account for so great a difference between the two fermentations that we have just described? Probably, it was owing to some modification effected in the medium by the previous life of the bacteria, or to the special character of the vibrios used in impregnation. Or, again, it might have been due to the action of the air, which, under the conditions of our second experiment, was not absolutely eliminated, since we took no precaution against its introduction at the moment of filling our flask, and this would tend to facilitate the multiplication of anaËrobian vibrios, just as, under similar conditions, would have been the case if we had been dealing with a fermentation by ordinary yeast. 144.In this case the liquid was composed as follows:—a saturated solution of lactate of lime, at a temperature of 25° C. (77° F.) was prepared, containing for every 100 c.c. (3-½ fl. oz.) 25·65 grammes (394 grains) of the lactate, C6H5O5CaO [new notation, C6H10CaO6]. This solution was rendered very clear by the addition of one gramme of phosphate of ammonia and subsequent filtration. For a volume of 8 litres (14 pints) of this clear, saturated solution, we used [1 gramme = 15·43 grains]:—
145.[1 millimetre = 0·039 inch: hence the dimensions indicated will be—length, from 0·00039 to 0·00117, or even 0·00176 in.; diameter, from 0·000058 to 0·000078, rarely 0.000117 in.] 146.The carbonaceous supply, as we remarked, had failed them, and to this failure the absence of vital action, nutrition, and multiplication was attributable. The liquid, however, contained butyrate of lime, a salt possessing properties similar to those of the lactate. Why could not this salt equally well support the life of the vibrios? The explanation of the difficulty seems to us to lie simply in the fact that lactic acid produces heat by its decomposition, whilst butyric acid does not, and the vibrios seem to require heat daring the chemical process of their nutrition. 147.To do this, it is sufficient first to fill the curved ends of the stop-cocked tubes of the flasks, as well as the india-rubber tube c c, which connects them, with boiling water that contains no air. 148.We find this fact, which we published as long ago as 1863, confirmed in a work of H. Hoffmann’s published in 1869, under the title MÉmoire sur les bactÉries, which has appeared in French (Annales des Sciences naturelles, 5th series, vol. xi.). On this subject we may cite an observation that has not yet been published. AËrobian bacteria lose all power of movement when suddenly plunged into carbonic acid gas; they recover it, however, as if they had only been suffering from anÆsthesia, as soon as they are brought into the air again. 149.These doubts might easily be removed by putting the matter to the test of direct experiment. 150.Robin, Sur la nature des fermentations, &c. (Journal de l’Anatomie et de la Physiologie, July and August, 1875, p. 386). 151.Liebig, Sur la fermentation et la source de la force musculaire (Annales de Chimie et de Physique, 4th series, t. xxiii. p. 5, 1870.) 152.It is important that we should here remark that, in the fermentation of pure solution of sugar by means of yeast, the oxygen originally dissolved in the water, as well as that appropriated by the globules of yeast in their contact with air, has a considerable effect on the activity of fermentation. As a matter of fact, if we pass a strong current of carbonic acid through the sugared water and the water in which the yeast has been treated, the fermentation will be rendered extremely sluggish, and the few new cells of yeast which form will assume strange and abnormal aspects. Indeed this might have been expected, for we have seen that yeast, when somewhat old, is incapable of development or of causing fermentation, even in a fermentable medium containing all the nutritive principles of yeast, if the liquid has been deprived of air; much more should we expect this to be the case in pure sugared water, likewise deprived of air. 153.Doebereiner, Journal de Chimie de Schweigger, vol. xii. p. 129, and Journal de Pharmacie, vol. i. p. 342. Mitscherlich, Monatsberichte d. KÖn. Preuss. Akad. d. Wissen. zu Berlin, and Rapports annuels de Berzelius, Paris, 1843, 3rd year. On the occasion of a communication on the inversion of cane sugar, by H. Rose, published in 1840, M. Mitscherlich observed: “The inversion of cane sugar in alcoholic fermentation is not due to the globules of yeast, but to a soluble matter in the water with which they mix. The liquid obtained by straining off the ferment on a filter paper, possesses the property of converting cane sugar into uncrystallizable sugar.” Berthelot, Comptes rendus de l’AcadÉmie. Meeting of May 28th, 1860. M. Berthelot confirms the preceding experiment of Mitscherlich, and proves, moreover, that the soluble matter of which that author speaks may be precipitated with alcohol without losing its invertive power. M. BÉchamp has applied Mitscherlich’s observation, concerning the soluble fermentative part of yeast, to fungoid growths, and has made the interesting discovery that fungoid growths, like yeast, yield to water a substance that inverts sugar. When the production of fungoid growths is prevented by means of an antiseptic the inversion of sugar does not take place. We may here say a few words respecting M. BÉchamp’s claim to priority of discovery. It is a well-known fact that we were the first to demonstrate that living ferments might be completely developed, if their germs were placed in pure water, together with sugar, ammonia, and phosphates. Relying on this established fact, that moulds are capable of development in sweetened water, in which, according to M. BÉchamp, they invert the sugar, our author asserts that he has proved that, “living organized ferments may originate in media which contain no albuminous substances.” (See Comptes rendus, vol. lxxv. p. 1519.) To be logical, M. BÉchamp might say that he has proved that certain moulds originate in pure sweetened water, without nitrogen or phosphates or other mineral elements, for such a deduction might very well be drawn from his work, in which we do not find the least expression of astonishment at the possibility of moulds developing in pure water, containing nothing but sugar without other mineral or organic principles. M. BÉchamp’s first Note on the inversion of sugar was published in 1855. In it we find nothing relating to the influence of moulds. His second, in which that influence is noticed, was published in January, 1858, that is, subsequently to our work on lactic fermentation, which appeared in November, 1857. In that work we established, for the first time, that the lactic ferment is a living organized being, that albuminous substances have no share in the production of fermentation, and that they only serve as the food of the ferment. M. BÉchamp’s Note was even subsequent to our first work on alcoholic fermentation, which appeared on December 21st, 1857. It is since the appearance of these two works of ours that the preponderating influence of the life of microscopic organisms, in the phenomena of fermentation, has been better understood. Immediately after their appearance M. BÉchamp, who, from 1855, had made no observation on the action of fungoid growths on sugar, although he had remarked their presence, modified his former conclusions. (Comptes rendus, January 4th, 1858.) 154.“There are two classes of ferments; the first, of which the yeast of beer may be taken as the type, perpetuate and renew themselves if they can find in the liquid in which they produce fermentation food enough for their wants; the second, of which diastase is the type, always sacrifice themselves in the exercise of their activity.” (Dumas, Comptes rendus de l’AcadÉmie, t. lxxv. p. 277, 1872.) 155.Fremy, Comptes rendus de l’AcadÉmie, vol. lviii. p. 1065, 1864. 156.See our Memoir of 1860 (Annales de Chimie et de Physique, vol. lviii.) p. 61, and following, and especially pp. 69 and 70, where the details of the experiment will be found. 157.Pasteur, Comptes rendus de l’AcadÉmie des Sciences, vol. lxxiii. p. 1419, 1871. 158.In his Memoir of 1870, Liebig has made a remarkable admission: “My late friend Pelouze,” he says, “had communicated to me, nine years ago, certain results of M. Pasteur’s researches on fermentation. I told him that, just then, I was not disposed to alter my opinion on the cause of fermentation, and that if it were possible by means of ammonia to produce or multiply the yeast in fermenting liquors, industry would soon avail itself of the fact, and that I would wait to see if it did so; up to the present time, however, there has not been the least change in the manufacture of yeast.” We do not know what M. Pelouze’s reply was; but it is not difficult to conceive so sagacious an observer remarking to his illustrious friend, that the possibility of deriving pecuniary advantage from the wide application of a new scientific fact had never been regarded as the criterion of the exactness of that fact. We could prove, moreover, by the undoubted testimony of very distinguished practical men, notably by that of M. Pezeyre, director of distilleries, that upon this point also Liebig was mistaken. 159.Pasteur, Comptes rendus de l’AcadÉmie, vol. lxxviii. pp. 213-216. 160.TrÉcul, Comptes rendus de l’AcadÉmie, vol. lxxviii. pp. 217, 218. 161.See on this subject the verbal observations which we addressed to the Academy of Sciences, at its meetings of April 10th and 24th, 1876. 162.M. Galland, a brewer in MaxÉville, near Nancy, published with his name, in November, 1875, a pamphlet, which was reproduced in the brewing journals of that date, bearing the title, It is said, “the air being impure, let us exclude it;” I say, “The air being impure, let us purify it.” These two aphorisms, together or apart, constitute the essential novelty of my researches on beer, and M. Galland is mistaken in attempting to appropriate the merit of the second alternative (see my note in the Comptes rendus of the 17th November, 1873, and the text of the letters-patent obtained 13th March of that year). M. Galland has devised some arrangements for putting the latter of these two schemes into practice; but it is possible, of course, to effect this in a variety of ways. M. Velten, a brewer in Marseilles, had already accomplished this in his efforts to carry out practically the procedure advocated in the present work. 163.[Non-technically, stirred about.—Ed.] 164.As stated in the paragraph on aËrobian ferments, in Chapter V., “low” yeasts, to be preserved in their state of “lowness,” must be submitted to often-repeated growths—every fifteen days in winter and every ten days in summer, that is to say, they must be grown afresh after each of these intervals. If this is done, there will be no reason to apprehend the formation of aËrobian ferments, which, as we have stated before, may embarrass us by transforming our “low” yeasts into “high” yeasts. 165.It has been observed by brewers that, sometimes, without any apparent cause, a yeast suddenly becomes inactive and fermentation ceases. Accidents of this kind may probably be explained in the same manner as the facts of which we are speaking. If a wort has not been aerated, or if it has been deprived of oxygen by a commencing development of microscopic organisms, the yeast formed in it will be very inferior, and the fermentation may stop at its commencement or soon afterwards. In such a case, an aeration of the yeast and wort would be the best remedy. 166.Pasteur, Comptes rendus de l’AcadÉmie des Sciences, vol. lii. p. 1260, and Études sur le Vin, 2nd Edition, p. 277. 167.We may here remark that the system of gutters in the above apparatus is much simpler than that described in connection with Figs. 76 and 77. The water which falls on the cover is carried off, when the gutter is full, by a circle of grooves, inclined so that the streams running from them meet and form more readily a sheet of water, which flows over the exterior surface of the cylindrical vessel. 168.[It will be well for the reader to bear in mind, that the word “strength,” used by Pasteur many times in this chapter, has a different meaning to that which attaches to it in the minds of English brewers, who in nearly every case use it in reference to original gravity, while the author employs it, in this chapter, at any rate, to denote the palate characteristic of strength, in other words palate-fulness. For this reason we have thought it best in many cases to actually substitute the term “palate-fulness,” or “body,” for the literal translation of the French word “force.”—F. F.] 169.[As some confusion has existed in the nomenclature of these salts, it may be as well to offer some explanation. The salt here used for absorbing oxygen was discovered by SchÜtzenberger, and named by him hydrosulphite of soda. It no longer now goes by that name, being called hyposulphite of soda, NaHSO2. The salts formerly known as hyposulphites are now called thiosulphates, as Na2S2O3. Thus to put them together we have:—
The thiosulphates were formerly regarded as containing the elements of water in their composition, thus:—Na2H2S2O4, which being halved would give NaHSO2, isomeric with hyposulphite, as Pasteur says. It is further to be observed that Pasteur uses the old notation, in which the number of atoms of sulphur and oxygen are the double of what they are in the new.—D. C. R.] 170.SchÜtzenberger, Comptes rendus de l’AcadÉmie des Sciences, vol. lxxv., p. 880. 171.M. SchÜtzenberger applies the term saturated to a solution of hydrosulphite prepared thus, or very nearly so; a current of sulphurous acid is passed through a solution of commercial bisulphite of soda, to excess; 100 c.c. (3-½ fl. oz.) of this solution and 30 grammes (46 grains) of zinc filings are put into a small flask, so as to completely fill it; the bottle is corked up and the mixture is shaken briskly for about a quarter of an hour. Lastly, the contents of this flask are poured into a large 2-litre flask, with water and containing milk of lime, prepared by mixing 100 grammes (3·2 troy oz.) of quicklime in the water just before it is used. The whole is shaken briskly for some minutes and then left to settle. The supernatant liquid soon becomes bright. This is the hydrosulphite; but in this state it is too concentrated; and should be syphoned into another 2-litre flask half full of water. In the alkaline condition this salt absorbs gaseous oxygen much less rapidly than in the acid, so that the liquids will retain their strength much longer, if they are kept in well-corked bottles. 172.The numbers n and n´´ will vary as the wort, or liquid which we have to test, is perfectly neutral or otherwise. Should it be acid n´´ n, should it be alkaline n n´´. This would be a very exact method of estimating the acidity or alkalinity of any coloured liquid. 173.[The Balling saccharometer being almost unknown in England, we may explain that its indications are for percentages of sugar in saccharine solutions, or of extract in worts; 17·9° Balling, therefore, means 17·9 per cent. of sugar or extract in the respective liquids.—F. F.] 174.Experiments made, at our request, by MM. Calmettes and Grenet, at Tantonville; in Tourtel’s brewery. 176.[For non-technical readers we may explain the expressions “gathered,” here used, and “turning out,” used on page 365. “Turning out” describes the operation of emptying the copper contents into the hop-back, or the hop-back contents on to the coolers. “Gathering” refers to the time when the worts are finally intermixed and weighed, prior to the commencement of vinous fermentation.—F. F.] 177.We know also from the direct experiments of M. SchÜtzenberger, performed on aerated water with which yeast had been mixed, that yeast causes all the oxygen in solution to disappear very quickly, so that hydrosulphite gives no evidence of a trace. (See SchÜtzenberger, Revue scientifique, vol. iii. (2), April, 1874). 178.[The bottling needle (foret  aiguille) is a contrivance for permitting a cork to be driven into a bottle completely filled with liquid, without bursting the bottle. It consists of a slightly-tapering iron pin about 1/8th inch in diameter and 2 inches in length, somewhat flattened, and slightly curved throughout its entire length, with a groove running down one side from end to end, the pin being jointed with a ring, like a common ring cork-screw. In using it the pin is driven into the bottle alongside the cork, thus allowing the excess of liquid to escape as the cork advances. When the cork is completely home, the needle is withdrawn, and the elasticity of the cork enables it to fill up the space left, so that we have the bottle corked air-tight, and no air left between the cork and liquid.—D. C. R.] 179.We have remarked in our observations on No. 6 of Plate I. (p. 6) that amongst the amorphous granular deposits of wort and beer we often find minute balls of resinous and colouring matter, perfectly spherical and very dense, which if the liquids be shaken up will render them very turbid, but which readily and rapidly deposit again, without remaining in suspension in the least. Such then is the form in which the deposits of wort in course of fermentation are precipitated, when the wort has been freely exposed to oxygen. One day in the laboratory we were desirous of starting a fermentation in a vessel capable of holding 12 hectolitres (264 gallons). But as we only had at our disposal a copper capable of holding 2-½ hectolitres, we procured the wort from a neighbouring brewery in two barrels of 6 hectolitres each. This wort we re-heated, in portions, in our 2-½ hectolitre copper, a treatment which had the effect of oxidizing the wort more than it would have been in the brewery. In this case the beer fell remarkably bright, and the cells of yeast were accompanied by the deposit of minute agglomerations sketched in Plate I., No. 6. We have repeated this experiment on a smaller scale and have obtained the same result. 180.It is evident that this arrangement may be modified in many ways. Any of the ordinary worms, or, generally speaking, any of the more modern refrigerators invented during the last few years, may be adopted. The only point that is of importance is the preservation of the purity of the wort during cooling. The Baudelot refrigerator is extensively adopted in France; for this reason we used it in our experiments at Tantonville. We might equally well, by enclosing the worm in a casing of sheet iron or tinned copper, pass our wort over the exterior of the tubes, the cold water passing through them. The wort would cool quicker in this way than with the arrangement described in the text, and if we arrange to admit only pure air into the case, always under conditions of purity. The aeration, moreover, could be made as much as we wished. 181.This arrangement limits the proportion of oxygen that may be introduced into the wort by direct oxidation. But it would be easy to increase this at will, by causing the wort as it comes from the copper and the hop-back to pass into a cylinder turning horizontally on its axis and furnished with blades fixed inside, so as to divide the wort and bring it better into contact with the air in the cylinder. Instead of a revolving cylinder we might use a fixed vessel, in which the wort could be stirred up by some arrangement outside. In either case we should have to take care that the air was pure when it came into contact with the wort, but this would be a matter of no difficulty; we would simply have to make communication with the outer air by means of a tube filled with cotton wool. Any air that might be in the vessel at the moment when the wort was introduced would be purified by the high temperature of the wort coming from the copper. We should, moreover, gain the great advantage of being able to bring oxygen to bear on our wort in determinate amounts. From this vessel it would pass on to the refrigerator. We might again raise the wort oxidized on the coolers to a temperature of 75° C. (167° F.), to recool it in this manner and aerate it by means of the pure-air pipe. 182.One of the barrels of the brewery beer was bottled about the end of October, at the same time that a barrel of M was. 184.The evaporation on the coolers varies according to the arrangements in different breweries; but in no case is it less than several hundredths of the total volume. One special advantage of the new process is that it gives us, ceteris paribus, a volume of beer that is 5, 6, or 7 per cent. greater than that which we should obtain by the old process, without in any way affecting the strength of the beer. It is easy to ascertain the quantity that evaporates on the coolers, by determining the quantity of water that must be added to a known volume of wort coming from the coolers to bring its density back exactly to that of the original wort, both being calculated to the same temperature. Bate’s English saccharometer, which shows differences of nearly 1/1000th in density, may be employed with advantage in this determination. 185.See Comptes rendus, vol. lxi., p. 734, 1863.
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