What is this terrible disease which every few years travels from the banks of the Indian Ganges, where it is always present, and makes its way to one or more of the great cities of Europe, killing its thousands with horrifying rapidity? The word “cholera” is used by the great Greek physician of antiquity, Hippocrates, and by his followers down to the days of our own Sydenham, to describe a malady which occurs commonly in summer, is often of severe character, but rarely fatal, and is characterised by the exudation from the walls of the intestine of copious fluid, usually accompanied by vomiting and sometimes by “cramps.” This malady is now distinguished by physicians as “simple cholera,” or European cholera, the last name being misleading, since the disease occurs all over the world. It is caused by a special microbe, which multiplies in the intestines and produces a poison. Other microbes produce similar results. One which causes luminosity in foul salt water has been found to produce cholera-like results when cultivated in a state of purity and swallowed by man. Other poisons besides those produced by microbes set up a sort of “cholera” in animals and man. Drugs of both mineral and vegetable origin have this effect, as every one knows, and are used in small quantities to produce purging. Microbes which are noted for other obvious effects which they produce by the poisons they form in man’s intestines—such as the microbe of typhoid fever—also produce cholera-like purging.

But the name “cholera,” or “the cholera,” is now applied without any further qualification to what would be more correctly described as “Indian cholera,” or “epidemic cholera.” It is a disease which first became known to Europeans in India in 1817, less than a hundred years ago. It resembles “simple” cholera in its general features, but is usually much more violent in its attack, and often causes complete collapse in two or three hours from its onset, and death in as many more. The main point about it is, however, that it is a quickly spreading “epidemic” disease; it invades a whole population, and travels from place to place along definite routes. Although the outbreak of cholera in India in 1817 was the first to attract the attention of Europeans, it was nothing new in India, and was recognised in distant ages by Hindu writers. Its usual name on the delta of the Ganges is “medno-neidan.” Ninety per cent. of the population perished of cholera in some districts of India in 1817, and English troops were attacked by it with terrible results.

Cholera gradually made its way in subsequent years through Persia to Russia, and at last to Western Europe; but it was not until late in the year 1831 that Indian cholera arrived for the first time in England, and in the following year it caused something like a panic. There have been at least three subsequent outbursts of Indian cholera (before that of the year 1908) which have reached Europe, and two of these have reached England and caused profound alarm and anxiety. That in 1854 reached us just before the Crimean War, and caused such rapid and numerous deaths in London, especially in the West End (St. James’s, Westminster), that the corpses were removed in carts as in the days of the plague. It was then that the Broad Street pump became famous, and the carefully demonstrated history of a cesspool leaking into the well of the pump, of the existence of a cholera patient in the house to which the cesspool was attached and of the infection with cholera of healthy people who sent all the way from Hampstead to fetch what they thought was the beautifully pure, cool, and palatable water of Broad Street, St. James’s, caused a most vivid and salutary impression on the public mind. The “water-carriage” of the cholera infection was established as a fact, and the subsequent abolition of surface wells and pumps, as well as of cesspools, in London and other cities was the result. Indeed, the active development of sanitation and sanitary measures of all kinds in Great Britain may be traced to the panic caused by the cholera in 1854 and to the well-founded conviction that it was in the power of the community, by the construction of sewers and the provision of untainted water-supply, to protect itself against such disaster in the future.

Years passed by, and still the actual germ of cholera was unknown. In India it was not even admitted that its diffusion was especially connected with water-supply. The methods of observing with the microscope those minute swarming organisms which are called “bacteria” became immensely improved. They were isolated, cultivated in purity, and the activity of a vast number of different kinds of different shapes, sizes, and modes of growth was ascertained. They were distinguished according to their shape as bacilli, spirilla, micrococci, and so on, and separate kinds were characterised—one producing ordinary putrefaction, another the souring of milk, another the “cheesing” of the same fluid, another the destruction of teeth and of bone, another the terrible anthrax of cattle or wool-sorters’ disease, another (a spiral thread in the blood this!) the recurrent fever of East Europe—each producing its own special poison or other chemical substance.

So it went on till Koch, of Berlin, discovered the bacillus of tubercle and Hansen that of leprosy. Others had failed to find what Koch now found as the result of a special mission on behalf of the German Imperial Government to India (undertaken as nearly as I can recollect about the year 1884)—namely, the living organism (Fig. 46) which by its growth in man’s intestine causes Indian cholera. Koch found a spiral threadlike “bacterium” in cholera patients, which readily breaks up into little curved segments like a comma (each less than the one ten-thousandth of an inch in length), and swarms by the million in the intestines of such patients. He showed that it can be cultivated in dilute gelatinised broth, and obtained in spoonfuls. It was, however, only with great difficulty that he could produce cholera in animals by administering this pure concentrated growth of cholera germs to them.

Then a most courageous thing was done. A great and very acute investigator of cholera in Munich, Pettenkofer by name—who did not believe that Koch’s comma-bacillus was really the effective germ of cholera—himself swallowed a whole spoonful—many millions—of the cultivated cholera germ. His assistants did the same—and none of them suffered any ill effect! Few, if any, of the investigators of this question gave up, as a consequence, their conviction that Koch’s bacillus was the real and active cause of cholera. They supposed that it must be necessary for the human intestine to be in a favourable condition—an unhealthy condition—for the Koch’s bacillus to multiply in it. It was by this time known that bacteria of all kinds are exceedingly sensitive in regard to the acidity or alkalinity, the oxygenation or de-oxygenation of the fluids and organic substances in which they can, when exactly suited, multiply with tremendous rapidity. Thus the tubercle bacillus cannot be cultivated on pure blood-serum, but if a trace of glycerine be added to the serum the tubercle bacillus grows, divides, multiplies like yeast in a brewing-vat. A little later Pettenkofer’s audacious experiment was repeated by Dr. Metchnikoff in Paris. He swallowed a cultivated mass of the cholera germ on three successive days, and had no injurious result. Others in his laboratory did the same, with the result of only a slight intestinal disturbance. But of a dozen who thus put the matter to the proof in the Institut Pasteur, one individual acquired an attack of true Indian cholera, accompanied by all the most violent symptoms, which very nearly caused his death. This experiment put an end to all discussion, and demonstrated, once for all, that the comma-bacillus (or spirillum) of Koch is really capable of producing Indian cholera, and is the actual agent of this disease.

The circumstances which determine whether the cholera-bacillus, when it gets into the human intestine, will develop and cause an attack of cholera, or will simply be digested or will remain alive, but inactive, for a time, have yet to be exactly determined. Obviously a knowledge of them must be of immense importance. Certain experiments show that other minute parasitic organisms—especially those called Sarcina (Fig. 46, e), which often, but by no means always, are abundant in the human intestine—favour the growth of the cholera-bacillus—in fact, prepare the ground or soil, as we may call it, for that deadly organism. This has been shown experimentally by sowing cholera-bacillus on plates of slightly acid gelatine, or jelly. It will not grow on this, but if at certain points on the surface of the jelly the Sarcina organism is planted, then it is found that all around the points where the Sarcina is growing the cholera-bacillus also flourishes and multiplies. And it seems probable that, just as there are microbes which are adjuvant or helpful to the cholera microbe, so there are others which are repressive or destructive of it. We know that this is the case with regard to some other microbes—namely, that a microbe which will flourish abundantly on a prepared jelly if it is alone, is entirely repressed and arrested in its growth by the presence of one other ascertained kind. It is, in fact, thus that some of the commoner putrefactive kinds of microbes occurring in river water are repressive of the typhoid-bacillus, which, if it should get there, flourishes best in the purest water or in water containing no other microbe. There is some ground for thinking that in certain districts there may be microbes present which make their way into the human intestine, and then actually repress the cholera-bacillus, should it subsequently be taken in with food or water. It would, of course, be of immense importance to discover such a microbe, if it exist, and the inquiry is at the present moment proceeding in Paris.

A very striking and at first sight astonishing fact in regard to this subject is that there are a very large number and variety of microbes habitually present in the human digestive tract. There are so many different kinds—differing altogether from one another in their chemical action—which are present in greater or less abundance in this tract from one end to the other, that no one is at present able to say even approximately how many there are, nor to give anything like a complete account of their properties. The fact is that their isolation and study, and the definite determination of their properties, is not an easy job. Many workers are engaged on it, and it will be years before the matter is threshed out. One most curious result of these studies is that a person may have the cholera-bacillus in his intestine—not growing with any activity, but still alive—and yet be perfectly well. He can, therefore, carry the cholera-bacillus from one locality to another and spread the disease, and yet be entirely devoid of suspicion, free himself from disease, and certified as healthy! The same is true of the bacillus of typhoid fever. Persons who have had typhoid fever have been shown to retain the typhoid-bacillus flourishing for as long as fourteen years afterwards in their intestine, without any ill effects to themselves, and to have been the constant source of infection and disease to those living in the same house with them by spreading the bacillus. The classical case of this is that of a woman who carried on a baker’s business at Strasburg. Infection by and protection from microbes is by no means so simple a thing as it is sometimes represented to be.

Now that we are quite sure as to Koch’s comma-bacillus, or spirillum, being the definite poison-producing agent causing Indian cholera, it is comparatively easy to understand its mode of dispersal and infection, and consequently how to avoid its attack. It is cultivated in the laboratories devoted to the study of such matters—kept in confinement, so to speak, for ten years and more—and its properties and conditions of life are well known. For instance, it is destroyed by “dryness,” hence it cannot be carried in a living infective state as “dust” in the air. It is also destroyed by exposure to a heat a good deal below that of boiling water, so that water itself can be freed from it by boiling, and food dipped in boiling (or nearly boiling) water, or heated on a metal tray beneath which a spirit or gas flame is burning, can be rendered safe just before it is swallowed, even when cholera is rife in the neighbourhood. Ordinary lime is a great destroyer of the bacillus, and can be used on a large scale to abolish it in refuse.

When the cholera is near one cannot be too scrupulously clean. The fingers must be carefully washed with antiseptic before a meal, and everything purified by heat only a few moments before being put into the mouth, since flies and careless handling may soil food or anything else exposed in a cool condition even for a few minutes. It is best when cholera is actually present in the house or town in which you live to swallow nothing which has been allowed to get cool; everything should be heated and eaten when hot. Mephistopheles, in Goethe’s Faust, complains of the swarming, pullulating life on the earth. He—the great destroyer—says:

The version is Sir Theodore Martin’s. Mephistopheles might be a bacteriologist explaining the difficulty of dealing with disease germs. In any case, it is the Mephistophelian spirit of annihilation, and flame as its instrument, which man brings to his service in the contest with cholera germs.

The great carriers of cholera are human beings themselves travelling in caravans, pilgrimages, shiploads. For the fact has now been established that a man may harbour inside him the cholera-bacillus without its multiplying largely or rendering him seriously ill. Once it is brought by such an individual into a favourable locality, it is spread by water contaminated by him, and yet used for drink and domestic purposes; and also it is spread by his touching things in which the bacillus can grow, such as cooked food, fruits, etc., swallowed subsequently by unsuspecting purchasers or employers. You have, in order to avoid cholera (and similar infections), not only to have very clean fingers yourself, but to see to it that your servants’ fingers are clean also, or else that anything they touch is afterwards heated for a few minutes to near boiling-point before you let it enter your mouth. A little history illustrative of the need of this precaution is on record. In Egypt during a recent outbreak of cholera there was a very wealthy lady who lived alone in an isolated palace under the charge of a physician. She had a delicate appetite; her food was most carefully prepared. She drank and used only boiled sterilised water; no one was allowed to approach her except her servants, who never left the palace grounds, and were in good health. She sickened of cholera and died. It was a puzzle as to how she had acquired the infection. Her physician at last discovered that she daily partook of cold chicken-broth, prepared carefully by her cook. The cook, though practically well, was found to be infected with the cholera-bacillus, which had probably lodged in his intestine some weeks previously at the commencement of the outbreak of the disease in Egypt. Though living in him the cholera-bacilli had not found a favourable field of growth. This man in handling the cold broth, the cloth used to rub the spoon with which it was stirred, or the basin itself, had, it was found by making the actual experiment, been able to transfer the minute bacillus to the cold broth, a most favourable and nourishing medium for its growth, and so his isolated carefully guarded employer received an abundant crop of the bacilli and developed a fatal attack of cholera. Had the lady taken the broth hot, there would have been no living cholera-bacillus in it, and if she had thus guarded herself in regard to all food, by the use of heat and great cleanliness, she would have escaped infection.

The most interesting development of knowledge and speculation with regard to the microbes which infest the human intestine and other regions of the human body is (as I mentioned above) connected with the fact that one kind or species of microbe has the power of favouring the growth of another, if present alongside of it, and that another kind has the power of checking or antagonising its growth. Thus common putrefactive microbes of river water are hostile to the cholera-bacillus and to the typhoid-bacillus. Those disease-producing bacilli live longest and best in very pure water! Thus, too, it is found that the microbe of sour milk—the lactic-bacillus—is antagonistic to the common putrefactive microbe of the intestinal contents—the well-known bacillus coli. In virtue of the acid which it produces, the microbe of sour milk arrests the excessive growth and activity of the putrefactive bacillus coli. Hence the utility of sour milk in many cases of intestinal trouble. We contain within us a microbian flora of such variety and abundance of kinds and so nicely balanced in their antagonisms and co-operations in a healthy man, that one cannot wonder at the timidity of the medical man who hesitates to interfere with their conflicts and established modus vivendi. Yet that seems to be the direction in which action will have to be taken. It seems likely that in different localities—towns, forests, highlands, lowlands, seaboards—there are prevalent different microbes which enter the bodies of human visitors and act as disturbers of the native microbian flora previously established in the stranger.

That there are great differences in the microbian flora (including herein minute moulds and fungi as well as bacteria) of different localities, is shown by the great experiment of cheese-making which mankind carries on. Each kind of cheese—Stilton, Cheshire, Dutch, Roquefort, GruyÈre, Gorgonzola, etc.—is the result of the combined and successive action on milk of a vast number of microbes; and it is the fact that the combination which produces any given kind of cheese is only found and (unconsciously of the exact nature of what he is doing) brought into activity by man at certain places. You cannot make Cheshire cheese in France nor GruyÈre in Cheshire, and so on. It is suggested—and the matter is being pursued by experiment and observation at the present time in France—that possibly amongst the other things which go to make up the qualities of the air which agrees or disagrees with one in any given locality—are the local microbes. This must not be regarded as a conclusion which has been fully worked out—it is an ingenious and promising suggestion made by Metchnikoff as the result of some observations, and will be fully inquired into. The fact which I have mentioned above (p. 242)—that the presence of the microbe Sarcina favours the growth of the cholera-bacillus—indeed, enabling it to grow and flourish in conditions in which it was inert until the Sarcina was “sown” alongside of it—renders it worth investigating the question as to whether there are “local” germs or microbes which in this or that region are abundant and get into man’s food and drink, and so into his intestine, and become established there, helping or antagonising the growth of other microbes already there or subsequently introduced. Thus, to the various considerations in regard to the “air” of a locality, such as rarefaction, moisture, temperature, movement, ozone, and the perfumes and exhalations of pine trees, rosemary, and sweet-smelling grasses, which seem to be those which are the most likely to affect the health of inhabitants and visitors, it is not improbable that we must add the influence of an invisible local flora of microbes. The inquiry is a long and laborious one, but it will be carried through. The microbes, whether in air or water, or on the surfaces of things, can be collected by washing them into warm liquid gelatine. Then the gelatine is poured out on a plate, and hardens as a thin sheet of jelly. This is protected from all further contamination, and, after a few hours, each invisible microbe embedded immovably in the jelly makes itself apparent. It multiplies enormously whilst remaining stuck to one spot, and is no longer invisible, but presents itself to the eye as a little sphere, or disc, of characteristic shape, colour, and quality, consisting of many hundred thousands of crowded microbes produced by the growth and division of the original invisible one. Some dozens or some hundreds of little growing “dots,” and of many various kinds, will thus reveal themselves in the jelly according to the number and kinds of utterly invisible parent microbes introduced by your “washings” into the jelly. And so the investigator has the means of getting at each kind of invisible microbe quite detached from the others, and of separating it for further cultivation and experiment as to its chemical and disease-producing qualities. These microbial gardens of jelly-plates are, indeed, a wonderful revelation and a fitting “horticultural” accompaniment to the dark and gloomy forests of rampant wild microbes in our insides, where all are struggling for the soil, one crushing out another by its sheer exuberance, a third choked by the encircling luxuriance of a fourth, just as the trees, mosses, and climbers of a tropical jungle are budding, pushing, grasping, destroying one another in their irrepressible growth.

Pettenkofer, of Munich, when he found (as Metchnikoff did later) that the cholera-bacillus could be swallowed in spoonfuls without producing any harm, came to the conclusion that, though it was a necessary agent of the disease “cholera,” yet that there was still an unknown additional determining “cause” of a local character which must be present in order to render the “cholera-bacillus” effective. Metchnikoff is now seeking this “local” cause and parallel antagonistic causes, in the microbian flora of localities which locally effect an entry into the human body, and are, on the one hand, “favourable,” or on the other hand “antagonistic.” Take as a concrete example Versailles. When cholera has been rife in Paris, there has been no cholera at Versailles. There is something at or about Versailles which does not permit cholera to flourish in men who live there. The guess—the hypothesis—which is being investigated at this moment, is that there is possibly a microbe present at Versailles which enters into the microbial jungle of the intestine of mankind there, and is inimical to, repressive of, the cholera-bacillus when it also arrives there. Similarly, the suggestion is entertained, and is being experimentally tested, that there is in Paris a microbial inhabitant of the intestine which is favourable to the energetic growth of the cholera-bacillus when it puts in an appearance, but that this favouring (as yet undetermined) microbe does not exist at Versailles.

These imaginings and guesses as to favouring and antagonising microbes must not be confused with the definitely ascertained facts as to the cholera-bacillus. But they are quite sufficiently important and probable to justify their narration to a discreet and sympathetic public.