  § 1. Before AristotleWhat is science? It is a question that cannot be answered easily, nor perhaps answered at all. None of the definitions seem to cover the field exactly; they are either too wide or too narrow. But we can see science in its growth and we can say that being a process it can exist only as growth. Where does the science of biology begin? Again we cannot say, but we can watch its evolution and its progress. Among the Greeks the accurate observation of living forms, which is at least one of the essentials of biological science, goes back very far. The word Biology, used in our sense, would, it is true, have been an impossibility among them, for bios refers to the life of man and could not be applied, except in a strained or metaphorical sense, to that of other living things. The Greek people had many roots, racial, cultural, and spiritual, and from them all they inherited various powers and qualities and derived various ideas and traditions. The most suggestive source for our purpose is that of the Minoan race whom they dispossessed and whose lands they occupied. That highly gifted people exhibited in all stages of its development a marvellous power of graphically representing animal forms, of which the famous Cretan friezes, Vaphio cups (Fig. 5), For the earliest biological achievements of Greek peoples we have to rely largely on information gleaned from artistic remains. It is true that we have a few fragments of the works of both Ionian and Italo-Sicilian philosophers, and in them we read of theoretical speculation as to the nature of life and of the soul, and we can thus form some idea of the first attempts of such workers as Alcmaeon of Croton (c. 500 b. c.) to lay bare the structure of animals by dissection. Fig. 1. Lioness and young from an Ionian vase of the sixth century b. c. found at Caere in Southern Etruria (Louvre, Salle E, No. 298), from Le Dessin des Animaux en GrÈce d’aprÈs les vases peints, by J. Morin, Paris (Renouard), 1911. The animal is drawing itself up to attack its hunters. The scanty mane, the form of the paws, the udders, and the dentition are all heavily though accurately represented. Fig. 2. A, Jaw bones of lion; B, head of lioness from Caere vase (Fig. 1), after Morin. Note the careful way in which the artist has distinguished the molar from the cutting teeth. Something more is, however, revealed by early Greek Art. We are in possession of a series of vases of the seventh and sixth centuries before the Christian era showing a closeness of observation of animal forms that tells of a people awake to the study of nature. We have thus portrayed for us a number of animals—plants seldom or never appear—and among the best rendered are wild creatures; we see antelopes quietly feeding or startled at a sound, birds flying or picking worms from the ground, fallow deer forcing their way through thickets, browsing peacefully, or galloping away, boars facing the hounds and dogs chasing hares, wild cattle forming their defensive circle, hawks seizing their prey. Many of these exhibit minutely accurate observation. The very direction of the hairs on the animals’ coats has sometimes been closely studied, and often the muscles are well rendered. In some cases even the dentition has been found Fig. 3. Paintings of fish on plates. Italo-Greek work of the fourth century B. C. From Morin.
Animal paintings of this order are found scattered over the Greek world with special centres or schools in such places as Cyprus, Boeotia, or Chalcis. The very name for a painter in Greek, zoographos, recalls the attention paid to living forms. By the fifth century, in representing them as in other departments of Art, the supremacy of Attica had asserted itself, and there are many beautiful Attic vase-paintings of animals to place by the side of the magnificent horses’ heads of the Parthenon (Fig. 6). In Attica, too, was early developed a characteristic and closely accurate type of representation of marine forms, and this attained a wider vogue in Southern Italy in the fourth century. From the latter period a number of dishes and vases have come down to us bearing a large variety of fish forms, portrayed with an exactness that is interesting in view of the attention to marine creatures in the surviving literature of Aristotelian origin (Fig. 3). These artistic products are more than a mere reflex of the daily life of the people. The habits and positions of animals are observed by the hunter, as are the forms and colours of fish by the fisherman; but the methods of huntsman and fisher do not account for the accurate portrayal of a lion’s dentition, the correct numbering of a fish’s scales or the close study of the lie of the feathers on the head, and the pads on the feet, of a bird of prey (Fig. 4). With observations such as these we are in the presence of something worthy of the name Biology. Though but little literature on that topic earlier than the writings of Aristotle has come down to us, yet both the character of his writings and such paintings and pictures as these, suggest the existence of a strong interest and a wide literature, biological in the modern sense, antecedent to the fourth century. Fig. 4. Head and talons of the Sea-eagle, HaliaËtus albicilla:
Greek science, however, exhibits throughout its history a peculiar characteristic differentiating it from the modern scientific standpoint. Most of the work of the Greek scientist was done in relation to man. Nature interested him mainly in relation to himself. The Greek scientific and philosophic world was an Many wonders there be, but naught more wondrous than man: The light-witted birds of the air, the beasts of the weald and the wood He traps with his woven snare, and the brood of the briny flood. Master of cunning he: the savage bull, and the hart Who roams the mountain free, are tamed by his infinite art. And the shaggy rough-maned steed is broken to bear the bit. Sophocles, Antigone, verses 342 ff. (Translation of F. Storr.) It is thus not surprising that our first systematic treatment of animals is in a practical medical work, the pe?? d?a?t??, On regimen, of the Hippocratic Collection. This very peculiar treatise dates from the later part of the fifth century. It is strongly under the influence of Heracleitus (c. 540-475) and contains many points of view which reappear in later philosophy. All animals, according to it, are formed of fire and water, nothing is born and nothing dies, but there is a perpetual and eternal revolution of things, so that change itself is the only reality. Man’s nature is but a parallel to that of the universal nature, and the arts of man are but an imitation or reflex of the natural arts or, again, of the bodily functions. The soul, a mixture of water and fire, consumes itself in infancy and old age, and increases during adult life. Here, too, we meet with that singular doctrine, not without bearing on the course of later biological thought, that in the foetus all parts are formed simultaneously. On the proportion of fire and water in the body all depends, sex, temper, temperament, intellect. Such speculative ideas separate this book from the sober method of the more typical Hippocratic medical works with which indeed it has little in common. Much more important however for subsequent biological development, than such observations on the nature and habits of animals, is the service that the Hippocratic physicians rendered to Anatomy and to Physiology, departments in which the structure of man and of the domesticated animals stands apart from that of the rest of the animal kingdom. It is with the nature and constitution of man that most of the surviving early biological writings are concerned, and in these departments are unmistakable tendencies towards systematic arrangement of the material. Thus we have division and description of the body in sevens from the periphery to the centre and from the vertex to the sole of the foot, Fig. 5. MINOAN GOLD CUP. SIXTEENTH CENTURY b. c. Fig. 6. HORSE’S HEAD. FROM PARTHENON. 440 b. c. A little later, perhaps 390 b. c., is the treatise pe?? sa????, On muscles, which contains much more than its title suggests. It has the old system of sevens and, inspired perhaps by the philosophy of Heracleitus (c. 540-475), describes the heart as sending air, fire, and movement to the different parts of the body through the vessels which are themselves constantly in movement. The infant in its mother’s womb is believed to draw in air and fire through its mouth and to eat in utero. The action of air on the blood is compared to its action on fire. In contrast to some of the other Hippocratic treatises the central nervous system is in the background; much attention, however, is given to the special senses. The brain resounds during audition. The olfactory nerves are hollow, lead to the brain, and convey volatile substances to it which cause it to secrete mucus. The eyes also have been examined, and their coats and humours roughly described; an allusion, the first in literature, is perhaps made to the crystalline lens, and the eyes of animals are compared with those of man. There is evidence not only of dissection but of experiment, and in efforts to compare the resistance of various tissues to such processes as boiling, we may see the small beginning of chemical physiology. An abler work than any of these, but exhibiting less power of observation is a treatise, pe?? ?????, On generation, that may perhaps be dated about 380 b. c. The same interest that he exhibits for the development of man and animals he shows also for plants. ‘A seed laid in the ground fills itself with the juices there contained, for the soil contains in itself juices of every nature for the nourishment of plants. Thus filled with juice the seed is distended and swells, and thereby the power (= faculty ? d???a??) diffused in the seed is compressed by living principle (pneuma) and juice, and bursting the seed becomes the first leaves. But a time comes when these leaves can no longer get nourished from the juices in the seed. Then the seed and the leaves erupt, for urged by the leaves the seed sends down that part of its power which is yet concentrated within it and so the roots are produced as an extension of the leaves. When at last the plant is well rooted below and is drawing its nutriment from the earth, then the whole grain disappears, being absorbed, save for the husk, which is the most solid part; and even that, decomposing in the earth, ultimately becomes invisible. In time some of the leaves put forth branches. The plant being thus produced by humidity from the seed is still soft and moist. Growing actively both above and below, it cannot as yet bear fruit, for it has not the quality of force and reserve (d??a?? ?s???? ?a? p?a??) from which a seed can be Nor does our author hesitate to draw an analogy between the plant and the mammalian embryo. ‘In the same way the infant lives within its mother’s womb and in a state corresponding to the health of the mother ... and you will find a complete similitude between the products of the soil and the products of the womb.’ The early Greek literature is so scantily provided with illustrations drawn from botanical study, that it is worth considering the remarkable comparison of generation of plants from cuttings with that from seeds in the same work. ‘As regards plants generated from cuttings ... that part of a branch where it was cut from a tree is placed in the earth and there rootlets are sent out. This is how it happens: The part of the plant within the soil draws up juices, swells, and develops a pneuma (p?e?a ?s?e?), but not so the part without. The pneuma and the juice concentrate the power of the plant below so that it becomes denser. Then the lower end erupts and gives forth tender roots. Then the plant, taking from below, draws juices from the roots and transmits them to the part above the soil which thus also swells and develops pneuma; thus the power from being diffused in the plant becomes concentrated and budding, gives forth leaves.... Cuttings, then, differ from seeds. With a seed the leaves are borne first, then the roots are sent down; with a cutting the roots form first and then the leaves.’ But with these works of the early part of the fourth century the first But though the ethical view of nature overwhelmed science in the end, the advent of the mighty figure of Aristotle (384-322) stayed the tide for a time. Yet the writer on Greek Biology remains at a disadvantage in contrast with the Historian of Greek Mathematics, of Greek Astronomy, or of Greek Medicine, in the scantiness of the materials for presenting an account of the development of his studies before Aristotle. The huge form of that magnificent naturalist completely overshadows Greek as it does much of later Biology. § 2. AristotleWith Aristotle we come in sight of the first clearly defined personality in the course of the development of Greek biological thought—for the attribution of the authorship of the earlier Hippocratic writings is more than doubtful, while the personality of the great man by whose name they are called cannot be provided with those clear outlines that historical treatment demands. Aristotle was born in 384 b. c. at Stagira, a Greek colony in the Chalcidice a few miles from the northern limit of the present monastic settlement of Mount Athos. His father, Nicomachus, was physician to Amyntas III of Macedonia and a member of the guild or family of the Asclepiadae. From Nicomachus he may have inherited his taste for biological investigation and acquired some of his methods. At seventeen Aristotle became a pupil of Plato at Athens. After Plato’s death in 347 Aristotle crossed the Aegean to reside at the court of Hermias, despot of Atarneus in Mysia, whose niece, Pythias, he married. It is not improbable that the first draft of Aristotle’s biological works and the mass of his own observations were made during his stay in this region, for in his biological writings much attention is concentrated on the natural history of the Island of Lesbos, or Mytilene, that lies close opposite to Atarneus. Investigation has shown that in the History of Animals there are frequent references to places on the northern and eastern littoral of the Aegean, and especially to localities in the Island of Lesbos; on the other hand places in Greece proper are but seldom mentioned. Fig. 7. ARISTOTLE From HERCULANEUM The scientific works to which Aristotle’s name is attached may be divided into three groups, physical, biological, and psychological. In size they vary from such a large treatise as the History of Animals to the tiny tracts which go to make up the Parva naturalia. So far as the scientific writings can be distinguished as separate works they may be set forth as follows:
In a general way it may be stated that the physical works, with which we are not here directly concerned, while they show ingenuity, learning, and philosophical power, yet betray very little direct and original observation. They have exerted enormous influence in the past and for at least two thousand years provided the usual physical conceptions of the civilized world both East and West. After the Galilean revolution in physics, however, they became less regarded and they are not now highly esteemed by men of science. The biological works of Aristotle, on the other hand, excited comparatively little interest during the Middle Ages, but from the sixteenth century on they have been very closely studied by naturalists. From the beginning of the nineteenth century, and especially as a result of the work of Cuvier, Richard Owen, and Johannes MÜller, Aristotle’s reputation as a naturalist has risen steadily, and he is now universally admitted to have been one of the very greatest investigators of living nature. The philosophical bases of Aristotle’s biology are mainly to be found Aristotle was a most voluminous author and his biological writings form but a small fraction of those to which his name is attached. Yet these biological works contain a prodigious number of first-hand observations and it has always been difficult to understand how one investigator could collect all these facts, however rapid his work and skilful his methods. The explanations that have reached us from antiquity are, indeed, picturesque, but they are neither credible in themselves nor are they consistent with each other. Thus Pliny writing about a. d. 77 says ‘Alexander the Great, fired by desire to learn of the natures of animals, entrusted the prosecution of this design to Aristotle.... For this end he placed at his disposal some thousands of men in every part of Asia and Greece, and among them hunters, fowlers, fishers, park-keepers, herds-men, bee-wards, as well as keepers of fish-ponds and aviaries in order that no creature might escape his notice. Through the information thus collected he was able to compose some fifty volumes.’ Now in all Aristotle’s works there is not a single sentence in praise of Alexander and there is some evidence that the two had become estranged. In support of this we may quote Plutarch (c. a. d. 100) who gives a detailed description of a conspiracy in 327 b. c. against Alexander by Callisthenes, a pupil of Aristotle who appears to have kept up a correspondence with his master. Nevertheless, remarkable as is Aristotle’s acquaintance with animal forms, investigation shows that he is reliable only when treating of creatures native to the Aegean basin. As soon as he gets outside that area his statements are almost always founded on hearsay or even on fable. When we turn to the Aristotelian biological works themselves we naturally inquire first into the question of genuineness, and here a difficulty arises in that all his extant works have come down to us in a state that is not comparable to those of any other great writer. Among the ancients admiration was expressed for Aristotle’s eloquence and literary powers, but, in the material that we have here to consider, very little trace of these qualities can be detected by even the most lenient judge. The arrangement of the subject-matter is far from perfect even if we allow for the gaps and disturbances caused by their passage through many hands. Moreover, there is much repetition This curious state of the Aristotelian writings has given rise to much discussion among scholars and to explain it there has been developed what is known as the ‘notebook theory’. It is supposed that the bases of the material that we possess were notebooks put together by Aristotle himself for his own use, probably while lecturing. These passed, it is believed, into the hands of certain of his pupils and were perhaps in places incomprehensible as they stood. Such pupils, after the master’s death, filled out the notebooks either from the memory of his teaching or from their own knowledge—or ignorance. Thus modified, however, they were still not prepared for publication, even in the limited sense in which works may be said to have been published in those days, but they formed again the fuller bases of notes for lectures delivered by his successors. In this form they have finally survived to our time, suffering, however, from certain further losses and displacements on a larger scale. Some of the ‘Aristotelian’ works are undoubtedly more deeply spurious, but the works that are regarded as ‘genuine’ do not seem to have been seriously tampered with, except by mere scribal or bookbinders’ blunders, at any date later than a generation or two following Aristotle’s own time. These notebooks as they stand are in fact probably in much the state in which we should find them were we able to retrieve a copy dating from the first or second century b. c. ‘Of things constituted by nature some are ungenerated, imperishable, and eternal, while others are subject to generation and decay. The former are excellent beyond compare and divine, but less accessible to knowledge. The evidence that might throw light on them, and on the problems which we long to solve respecting them, is furnished but scantily by sensation; whereas respecting perishable plants and animals we have abundant information, living as we do in their midst, and ample data may be collected concerning all their various kinds, if only we are willing to take sufficient pains. Both departments, however, have their special charm. The scanty conceptions to which we can attain of celestial things give us, from their excellence, more pleasure than all our knowledge of the world in which we live; just as a half glimpse of persons we love is more delightful than a leisurely view of other things, whatever their number and dimensions. On the other hand, in certitude and in completeness our knowledge of terrestrial things has the advantage. Moreover, their greater nearness and affinity to us balances somewhat the loftier interest of the heavenly things that are the objects of the higher philosophy.... For if some [creatures] have no graces to charm the sense, yet even these, by disclosing to intellectual perception the artistic spirit that designed them, give immense pleasure to all who can trace links of causation, and are inclined to philosophy. We therefore must not recoil with childish aversion from the examination of the humbler animals. Every realm of nature is marvellous. It is told of Heraclitus that when strangers found him warming himself at the kitchen fire and hesitated to go in, he bade them enter since even in the kitchen divinities were present. ‘If any person thinks the examination of the rest of the animal kingdom an unworthy task, he must hold in like disesteem the study of man. For no one can look at the primordia of the human frame—blood, flesh, bones, vessels, and the like—without much repugnance. Moreover, when any one of the parts or structures, be it which it may, is under discussion, it must not be supposed that it is its material composition to which attention is being directed or which is the object of the discussion, but the relation of such part to the total form.... ‘As every instrument and every bodily member subserves some partial end, that is to say, some special action, so the whole body must be destined to minister to some plenary sphere of action. Thus the saw is made for sawing, since sawing is a function, and not sawing for the saw. Similarly, the body too must somehow or other be made for the soul, and each part of it for some subordinate function to which it is adapted.’ Aristotle is, in the fullest sense a ‘vitalist’. He believes that the presence of a certain peculiar principle of a non-material character is essential for the exhibition of any of the phenomena of life. This principle we may call soul, translating his word ????. Living things, like all else in nature, have, according to Aristotle, an end or object. ‘Everything that Nature makes,’ he says, ‘is means to an end. For just as human creations are the products of art, so living objects are manifestly the products of an analogous cause or principle.... And that the heaven, if it had an origin, was evolved and is maintained by While putting his own view Aristotle does not fail to tell us of the standpoint of his opponents. ‘Why, however, it must be asked, should we look on the operations of Nature as dictated by a final cause, and intended to realize some desirable end? Why may they not be merely the results of necessity, just as the rain falls of necessity, and not that the corn may grow? For though the rain makes the corn grow, it no more occurs in order to cause that growth, than a shower which spoils the farmer’s crop at harvest-time occurs in order to do that mischief. Now, why may not this, which is true of the rain, be true also of the parts of the body? Why, for instance, may not the teeth grow to be such as they are merely of necessity, and the fitness of the front ones with their sharp edge for the comminution of the food, and of the hind ones with their flat surface for its mastication, be no more than an accidental coincidence, and not the cause that has determined their development?’ The answers to these questions form a considerable part of Aristotle’s philosophy where we are unable to follow him. For the limited field of biology, however, the question is on somewhat narrower lines. ‘What,’ he asks, ‘are the forces by which the hand or the body was fashioned into shape? The wood carver will perhaps say, by the axe or the There can be no doubt that through much of the Aristotelian writings runs a belief in a kinetic as distinct from a static view of existence. It cannot be claimed that he regarded the different kinds of living things as actually passing one into another, but there can be no doubt that he fully realized that the different kinds can be arranged in a series in which the gradations are easy. His scheme would be something like that represented on p. 30 (Fig. 7 a). ‘Nature,’ he says, ‘proceeds little by little from things lifeless to Fig. 7a. The Order of Living Things according to Aristotle. ‘A sponge, in these respects completely resembles a plant, in that ... it is attached to a rock, and that when separated from this it dies. Slightly different from the sponges are the so-called Holothurias ... as also sundry other sea-animals that resemble them. For these are free and unattached, yet they have no feeling, and their life is simply that ‘The Acalephae or Sea-nettles, ... lie outside the recognized groups. Their constitution, like that of the Tethya, approximates them on the one side to plants, on the other side to animals. For seeing that some of them can detach themselves and can fasten on their food, and that they are sensible of objects which come in contact with them, they must be considered to have an animal nature.... On the other hand, they are closely allied to plants, firstly by the imperfection of their structures, secondly by their being able to attach themselves to the rocks, which they do with great rapidity, and lastly by their having no visible residuum notwithstanding that they possess a mouth.’ Thus ‘Nature passes from lifeless objects to animals in such unbroken sequence, interposing between them beings which live and yet are not animals, that scarcely any difference seems to exist between two neighbouring groups owing to their close proximity.’ ‘The female does not contribute semen to generation but does contribute something ... for there must needs be that which generates and that from which it generates.... If, then, the male stands for the effective and active, and the female, considered as female, for the passive, it follows that what the female would contribute to the semen of the male would not be semen but material for the semen to work upon.... ‘How is it that the male contributes to generation, and how is it that the semen from the male is the cause of the offspring? Does [the semen] exist in the body of the embryo as a part of it from the first, mingling with the material which comes from the female? Or does the semen contribute nothing to the material body of the embryo but only to the power and movement in it?... The latter alternative appears to be the right one both a priori and in view of the facts.’ This discussion leads to the question of the natural process of generation itself. It is a topic that we have seen discussed by an The next question that arises is the mechanism by which the offspring come to resemble their parents. The mechanism in the case of inheritance from the father is comprehensible when we consider the origin and nature of the semen, but the inheritance from the mother requires further explanation. The view of Aristotle is based upon the nature of the catamenia and their disappearance during gestation. ‘The catamenia’, in his view, ‘are a secretion as the semen is.’ ‘For the same reason the development of the embryo takes place in the female; neither the male himself nor the female emits semen into the female, but the female receives within herself the share contributed by both, because in the female is the material from which is made the resulting product. Not only must the mass of material from which the embryo is in the first instance formed exist there, but further material must constantly be added so that the embryo may increase in size. Therefore the birth must take place in the female. For the carpenter must keep in close connexion with his timber and the potter with his clay, and generally all workmanship and the ultimate movement imparted to matter must be connected with the material concerned, as, for instance, architecture is in the buildings it makes.’ ‘Generation from the egg’, he says, ‘proceeds in an identical manner with all birds.... With the common hen after three days and nights there is the first indication of the embryo.... The heart appears like a speck of blood in the white of the egg. This point beats and moves as though endowed with life, and from it two vessels with blood in them trend in a convoluted course ... and a membrane carrying bloody fibres now envelops the yolk, leading off from the vessels.’ Aristotle lays considerable stress on the early appearance of the heart in the embryo. Corresponding to the general gradational view that he had formed of Nature, he held that the most primitive and fundamentally important organs make their appearance before the others. Among the organs all give place to the heart, which he considered ‘the first to live and the last to die’. A little later he observed that the body had become distinguishable, and was at first very small and white. ‘When an egg is ten days old the chick and all its parts are distinctly visible. The head still is larger than the rest of the body and the eyes larger than the head. At this time also the larger internal organs are visible, as also the stomach and the arrangement of the viscera; and the vessels that seem to proceed from the heart are now close to the navel. From the navel there stretch a pair of vessels, one [vitelline vein] towards the membrane that envelops the yolk, and the other [allantoic vein] towards that membrane which envelops collectively the membrane wherein the chick lies, the membrane of the yolk and the intervening liquid.... About the twentieth day, if you open the egg and touch the chick, it moves inside and chirps; and it is already coming to be covered with down when, after the twentieth day, the chick begins to break the shell.’ Aristotle recognized a distinction in the mode of development of mammals from that of all other viviparous creatures. Having divided the apparently viviparous animals into two groups, one of which is truly and internally and the other only externally viviparous, he pointed out that in the mammalia, the group regarded by him as internally viviparous, the foetus is connected until birth with the wall of the mother’s womb by the navel-string. These animals, in his view, produce their young without the intervention of an ovum, the embryo being ‘living from the first’. Such non-mammals, on the other hand, as are viviparous are so in the external sense only, that is, the young which he considered to arise in this group from ova may indeed develop within the mother’s womb and be born alive, but they go through their development without organic connexion with the mother’s body, so that her womb acts but as a nursery or incubator for her eggs. It was indeed a sort of accident among the ovipara whether in any particular species the ovum went through its development inside or outside the mother’s Yet though Aristotle regarded fish as an oviparous group, he knew also of kinds of fish that were externally viviparous. It is most interesting to observe, moreover, that he was acquainted with one particular instance among fish in which matters were less simple and in which the development bore an analogy to that of the mammalia, his true internal vivipara. ‘Some animals’, he says, ‘are viviparous, others oviparous, others vermiparous. Some are viviparous, such as man, the horse, the seal and all other animals that are hair-coated, and, of marine animals, the Cetaceans, as the dolphin, and the so-called Selachia.’ Aristotle tells us elsewhere that a species of these Selachia which he calls galeos—a name still used for the dog-fish by Greek fishermen—‘has its eggs in betwixt the [two horns of the] womb; these eggs shift into each of the two horns of the womb and descend, and the young develop with the navel-string attached to the womb, so that, as the egg-substance gets used up, the embryo is sustained to all appearances just as in quadrupeds. The navel-string is ... attached as it were by a sucker, and also to the centre of the embryo in the place where the liver is situated.... Each embryo, as in the case of quadrupeds, is provided with a chorion and separate membranes.’ The remarkable anatomical relationship of the embryo of Galeus (Mustelus) laevis to its mother’s womb was little noticed by naturalists until the whole matter was taken up by Johannes MÜller about 1840. Aristotle attempts to explain the viviparous character of the Selachians. His explanation has perhaps little meaning for the modern biologist, just as many of our scientific explanations will seem meaningless to our successors. But such explanations are often worth consideration not only as stages in the historical development of scientific thought, but also as illustrating the fact that while the ultimate object of science is a description of nature, the immediate motive of the best scientific work is usually an explanation of nature. Yet it is usually the descriptive, not the explanatory element that bears the test of time. ‘Birds and scaly reptiles’, says Aristotle, ‘because of their heat produce a perfect egg, but because of their dryness it is only an egg. The cartilaginous fishes have less heat than these but more moisture, so that they are intermediate, for they are both oviparous and viviparous within themselves, the former because they are cold, the latter because of their moisture; for moisture is vivifying, whereas dryness is farthest removed from what has life. Since they have neither feathers nor scales such as either reptiles or other fishes have, all of which are signs rather of a dry and earthy nature, the egg they produce is soft; for the earthy matter does not come to the surface in their eggs any more than in themselves. That is why they lay eggs in themselves, for if the egg were laid externally it would be destroyed, having no protection.’ This explanation is based on Aristotle’s fundamental doctrine of the opposite qualities, heat, cold, wetness, and dryness, that are found combined in pairs in the four elements, earth, air, fire, and water. Fig. 7b. The Four Elements and the Four Qualities. The theory of the elements and qualities is applicable to all matter and not specially to living things. The distinction between the living and not-living is to be sought not so much in its material constitution, but in the presence or absence of ‘soul’, and his teaching on that topic is to be found in his great work pe?? ?????, His belief as to the relationship of this soul to material things is a difficult and complicated subject which would take us far beyond the topics included in biological writings to-day, but he tells us that ‘there is a class of existent things which we call substance, including under that term, firstly, matter, which in itself is not this nor that; secondly, shape or form, in virtue of which the term this or that is at once applied; thirdly, the whole made up of matter and form. Matter is identical with potentiality, form with actuality,’ the soul being, in living things, that which gives the form or actuality. ‘Of natural bodies’, he continues, ‘some possess life and some do not: where by life we mean the power of self-nourishment and of independent growth and decay’. ‘The term life is used in various senses, and, if life is present in but a single one of these senses, we speak of a thing as living. Thus there is intellect, sensation, motion from place to place and rest, the motion concerned with nutrition, and, further, [there are the processes of] decay and growth,’ all various meanings or at least exhibitions of some form of life. Hence even ‘plants are supposed to have life, for they have within themselves a faculty and principle whereby they grow and decay.... They grow and continue to live so long as they are capable of absorbing nutriment. This form of life can be separated from the others ... and plants have no other faculty of soul at all,’ but The possession of one or more of the three types of soul, vegetative, sensitive, and rational, provides in itself a basis for an elementary form of arrangement of living things in an ascending scale. We have already seen that Aristotle certainly describes something resembling a ‘Scala Naturae’ and that such a scheme can easily be drawn up from passages in his works. It may, however, be doubted whether his phraseology is capable of extension so as to include a true classification of animals in any modern sense. It is true that he repeatedly divides animals into classes, Sanguineous and Non-sanguineous, Oviparous and Viviparous, Terrestrial and Aquatic, &c., but his divisions are for the most part simply dichotomic. He certainly defines a few groups of animals as the Lophura (Equidae), the Cete (Cetacea), and the Selache (Elasmobranchiae together with the Lophiidae) in a way that fairly corresponds to similar groups in later systems. In most cases, however, his definitions are not exact enough for modern needs, for the same animal may fall into more than one of his classes and widely different animals There are, however, scattered through the biological works, certain terms which are applied to animal groups and organs and are defined in such a way as to suggest that they might ultimately have been developed for classificatory purposes. Thus his lowest group is the species. ‘The individuals comprised within a single species (eÎd??) ... are the real existences; but inasmuch as these individuals possess one common specific form, it will suffice to state the universal attributes of the species, that is, the attributes common to all its individuals, once and for all.’ ‘But as regards the larger groups—such as birds—which comprehend many species, there may be a question. For on the one hand it may be urged that as the ultimate species represent the real existences, it will be well, if practicable, to examine these ultimate species separately, just as we examine the species Man separately; to examine, that is, not the whole class Birds collectively, but the Ostrich, the Crane, and the other indivisible groups or species belonging to the class. ‘On the other hand, this course would involve repeated mention of the same attribute, as the same attribute is common to many species, and so far would be somewhat irrational and tedious. Perhaps, then, it will be best to treat generically the universal attributes of the groups that ‘It is generally similarity in the shape of particular organs, or of the whole body, that has determined the formation of the larger groups. It is in virtue of such a similarity that Birds, Fishes, Cephalopoda, and Testacea have been made to form each a separate genus (?????). For within the limits of each such genus, the parts do not differ in that they have no nearer resemblance than that of analogy—such as exists between the bone of man and the spine of fish—but they differ merely in respect of such corporeal conditions as largeness smallness, softness hardness, smoothness roughness, and other similar oppositions, or, in one word, in respect of degree.’ The Aristotelian genus thus differs widely from the term as used in modern biology. In another passage he comes nearer to defining it and the analogy of parts which extends from genus to genus. ‘Groups that differ only in the degree, and in the more or less of an identical element that they possess are aggregated together under a single genus; groups whose attributes are not identical but analogous are separated. For instance, bird differs from bird by gradation, or by excess and defect; some birds have long feathers, others short ones, but all are feathered. Bird and Fish are more remote and only agree in having analogous organs; for what in the bird is Aristotle nowhere gives to his term genus a rigid application that can be applied throughout the animal kingdom. He uses the word in fact much as we should use the conveniently flexible term group, now for a larger and less definite, now for a smaller and more definite collection of species. This varying use of a technical word makes it impossible to draw up a classification based on his genera or indeed with any consistent use of the terms which he actually employs. The difficulty or impossibility of drawing up a satisfactory classificatory system from the Aristotelian writings has not, however, deterred numerous naturalists and scholars from making the attempt, and the subject has in itself a considerable history and literature
Some of the elements in this classification are fundamentally unsatisfactory in that they are based on negative characters. Such is the group of Anaima which is parallelled by our own equally convenient and negative though morphologically meaningless equivalent Invertebrata. Others, such as the subdivisions of the viviparous quadrupeds, can only be forcibly extracted out of Aristotle’s text. But there are yet others, such as the separation of the cartilaginous from the bony fishes, that exhibit true genius and betray a knowledge that can only have been reached by careful investigation. Remarkably brilliant too is his treatment of Molluscs. There can be no doubt that he dissected the bodies and carefully watched the habits of octopuses and squids, Malacia as he calls them. He separates them too far from the other Molluscs, grouped by him as Ostracoderma, but his actual descriptions of the structure and sexual process of the cephalopods are exceedingly remarkable, and after being long disregarded or misunderstood were verified and repeated in the course of the nineteenth century. Passing from his general ideas on the nature and division of living creatures we may turn to some of the most noteworthy of his actual observations. In the realm of comparative anatomy proper we may instance that of the stomach of ruminants. He must have dissected these animals, for he gives a clear and correct account of the four chambers. A very famous example in the Aristotelian works anticipating modern biological knowledge is afforded by his reference to the mode of reproduction of the cephalopods. ‘The Malacia such as the octopus, the sepia, and the calamary, have sexual intercourse all in the same way; that is to say, they unite at the mouth by an interlacing of their tentacles. When, then, the octopus rests its so-called head against the ground and spreads abroad its tentacles, the other sex fits into the outspreading of these tentacles, and the two sexes then bring their suckers into mutual connexion. Some assert that the male has a kind of penis in one of his tentacles, the one in which are the largest suckers; and they further assert that the organ is tendinous in character growing attached right up to the middle of the tentacle, and that the latter enables it to enter the nostril or funnel of the female.’ The reproductive processes of the Cephalopods were unknown to modern naturalists until the middle of the nineteenth century. Before that time several observers had noted the occasional presence of a peculiar parasite in the mantle cavity of female cephalopods and had described its supposed structure without tracing any relationship to the process of generation. In 1851 it was first shown that this supposed parasite was the arm of the male animal specially modified for reproductive Aristotle is perhaps at his best and happiest when describing the habits of living animals that he has himself observed. Among his most pleasing accounts are those of the fishing-frog and torpedo. In these creatures he did not fail to notice the displacement of the fins associated with the depressed form of the body. ‘In marine creatures,’ he says, ‘one may observe many ingenious devices adapted to the circumstances of their lives. For the account commonly given of the frog-fish or angler is quite true; as is also that of the torpedo.... ‘In the Torpedo and the Fishing-frog the breadth of the anterior part of the body is not so great as to render locomotion by fins impossible, but in consequence of it the upper pair [pectorals] are placed further back and the under pair [ventrals] are placed close to the head, while to compensate for this advancement they are reduced in size so as to be smaller than the upper ones. ‘In the Torpedo the two upper fins [pectorals] are placed in the tail, and the fish uses the broad expansion of its body to supply their place, each lateral half of its circumference serving the office of a fin.... The torpedo narcotizes the creatures that it wants to catch, overpowering them by the force of shock that is resident in its body, and feeds upon them; it also hides in the sand and mud, and catches all the creatures that swim in its way and come under its narcotizing influence. This phenomenon has been actually observed in operation.... The torpedo-fish is known to cause a numbness even in human beings. ‘The frog-fish has a set of filaments that project in front of its eyes; they are long and thin, like hairs, and are round at the tips; they lie on either side, and are used as baits.... The little creatures on which this fish feeds swim up to the filaments, taking them for bits of seaweed such as they feed upon. Accordingly, when the frog-fish stirs himself up a place where there is plenty of sand and mud and conceals himself therein, it raises the filaments, and when the little fish strike against them the frog-fish draws them in underneath into its mouth.... That the creatures get their living by this means is obvious from the fact that, whereas they are peculiarly inactive, they are often caught with mullets, the swiftest of fishes, in their interior. Furthermore, the frog-fish is usually thin when he is caught after losing the tips of his filaments.’ The modification of the musculature of the torpedo-fish for electric purposes and the fishing habits of the fishing-frog or Lophius are now well known, but it was many centuries before naturalists had confirmed the observations of the father of biology. When we turn from Aristotle’s observations in the department of natural history to his discussion of the actual mechanism of the living body, the subject now contained under the heading Experimental Physiology, we are in the presence of much less satisfactory material. Aristotle here exhibits his weakness in physics and not being endowed with any experimental knowledge of that subject his physiological development is very greatly handicapped. He seems often to accept fancies of his own in place of generalizations from collated observations. This tendency of his was conveyed to his successors and delayed physiological advance for many centuries. It forms a striking contrast to the method of An important factor in Aristotle’s physical and physiological teaching is the doctrine that matter is continuous and not made up of indivisible parts. He thus rejected the atomic views of his predecessors Leucippus and Democritus which have been preserved for us by the poem of Lucretius. The different kinds of matter existing merely in their state of simple mixture formed various uniform or homogeneous substances, homoeomeria, of which the tissues of living bodies provided one type. We now consider tissues as having structure made up of living cells or their products, but to Aristotle their structure was an essential fact following on their particular elemental constitution. The structure of muscle or flesh was perhaps comparable to that of a crystalline substance, for, as we have seen, Aristotle made no fundamental distinction between organic and inorganic substances, which are in his view alike subject to the processes of generation and corruption. The difference between them lies not in their structure but in their potential relation to the various degrees of soul, the vegetative, the animal, and the rational. ‘There are’, says Aristotle, ‘three degrees of composition, and of these the first in order is composition out of what some call the elements, earth, air, water, and fire.... ‘The second degree of composition is that by which the homogeneous parts of animals (????e??), such as bone, flesh, and the like, are constituted out of [these] primary substances. ‘The third and last stage is the composition which forms the The distinctions are not altogether clear but may perhaps be explained along such lines as the following. The division into homogeneous and heterogeneous corresponds in a general way to the later division into Tissues and Organs, the former, however, including much that we should not call tissue. The homogeneous parts were again of two kinds: (a) simple tissues or stuffs without any notion of size or shape, that is, mere substance capable of endowment with life or soul, e.g. cartilaginous or osseous tissues; and (b) simple structure, that is actual structure made of such a single tissue but with definite form and size, matter to which form had been added and which either was actually or had been endowed with soul, e.g. a cartilage or a bone. As a physiologist Aristotle is, in fact, in much the same position as he is as a physicist. He never dissected the human body, he had only the roughest idea of the course of the vessels, and his description of the vascular system is so difficult and confused that a considerable literature has been written on its interpretation. He regarded the heart as the central organ of the body and the seat of sensation and he probably believed that the arteries contained air as well as blood. He made no adequate distinction between veins and arteries. He tells us that two great vessels arise from the heart and that the heart is, as it were, a part of these vessels. The two vessels are apparently the aorta and the vena cava, and a very elementary and not very accurate description is given of the branches of these vessels. He believed that the heart had three chambers or cavities and that it took in air direct from the lung. The brain was for him mainly an organ by which were secreted certain In general we may say that his physiology is on a much lower plane than his natural history, since in dealing with physiological questions he always seems to have in mind the body as a whole and seldom pauses for any detailed investigation of a particular part. The physiological views of Aristotle were far from being fully accepted even by the generation which followed him. There was already growing up a school of physiologists whose work culminated five centuries later in that of Galen, where we find quite other views of the bodily functions. It is these views which we may take as more typical of the bases of Greek physiology (see p. 66). In much of the Aristotelian material that we have discussed we have seen the development of a class of interests very foreign to those of the modern biologist, in whose work the general discussion of the ultimate nature and origin of life seldom plays a large part. The business of the modern biologist is mainly with vital phenomena as he encounters them and he is not concerned with the deeper philosophical problems. The man of science considers a part of the Universe where the philosopher makes it his business to regard the whole. With Aristotle this modern scientific process of taking a part of the sensible Universe, such as a particular group of animals or the particular action of a particular organ, and considering it in and by and for itself without reference to other things, had not yet fully emerged. This is at least his theoretical view. But besides being a philosopher by choice he was a supreme naturalist by his natural endowments and he cannot suppress his love for nature and his capacity for observation. We see Aristotle the naturalist at his greatest as a direct observer or when reasoning directly about the observations that he has made. When he disregards his own observations and begins to erect theories on the observations or the views of others, he becomes weaker and less comprehensible. § 3. After AristotleAll Aristotle’s surviving biological works refer primarily to the animal creation. His work on plants is lost or rather has survived as the merest corrupted fragment. We are fortunate, however, in the possession of a couple of complete works by his pupil and successor Theophrastus (372-287), which may not only be taken to represent the Aristotelian attitude towards the plant world, but also give us an inkling of the general state of biological science in the generation which succeeded the master. These treatises of Theophrastus are in many respects the most complete and orderly of all ancient biological works that have reached our time. They give an idea of the kind of interest that the working scientist of that day could develop when inspired rather by the genius of a great teacher than by the power of his own thoughts. Theophrastus is a pedestrian where Aristotle is a creature of wings, he is in a relation to the master of the same order that the morphologists of the second half of the nineteenth century were to Darwin. For a couple of generations after the appearance of the Origin of Species in 1859 the industry and ability of naturalists all over the world were occupied in In the absence of any adequate system of classification, almost all botany until the seventeenth century consisted mainly of descriptions of species. To describe accurately a leaf or a root in the language in ordinary use would often take pages. Modern botanists have invented an elaborate terminology which, however hideous to eye and ear, has the crowning merit of helping to abbreviate scientific literature. Botanical writers previous to the seventeenth century were substantially without this special mode of expression. It is partly to this lack that we owe the persistent attempts throughout the centuries to represent plants pictorially in herbals, manuscript and printed, and thus the possibility of an adequate history of plant illustration. Theophrastus seems to have felt acutely the need of botanical terms, and there are cases in which he seeks to give a special technical meaning to words in more or less current use. Among such words are carpos = fruit, pericarpion = seed vessel = pericarp, and metra, the word used by him for the central core of any stem whether formed of wood, pith, or other substance. It is from the usage of Theophrastus that the exact definition of fruit and pericarp has come down to us. Theophrastus understood the value of developmental study, a conception derived from his master. ‘A plant’, he says, ‘has power of germination in all its parts, for it has life in them all, wherefore we should regard them not for what they are but for what they are becoming.’ ‘Some germinate, root and leaves, from the same point, some separately from either end of the seed. Thus wheat, barley, spelt, and all such cereals [germinate] from either end, corresponding to the position [of the seed] in the ear, the root from the stout lower part, the shoot from the upper; but the two, root and stem, form a single continuous whole. The bean and other leguminous plants are not so, but in them root and stem are from the same point, namely, their place of attachment to the pod, where, it is plain, they have their origin. In some cases there is a process, as in beans, chick peas, and especially lupines, from which the root grows downward, the leaf and stem upward.... In certain trees the bud first germinates within the seed, and, as it increases in size, the seeds split—all such seeds are, as it were, in two halves; again, all those of leguminous plants have plainly two lobes and are double—and then the root is immediately thrust out. But in cereals, the seeds being in one piece, this does not happen, but the root grows a little before [the shoot]. ‘Barley and wheat come up monophyllous, but peas, beans, and chick peas polyphyllous. All leguminous plants have a single woody root, from which grow slender side roots ... but wheat, barley, and the other There can be no doubt that here is a piece of minute observation on the behaviour of germinating seeds. The distinction between dicotyledons and monocotyledons is accurately set forth, though the stress is laid not so much on the cotyledonous character of the seed as on the relation of root and shoot. In the dicotyledons root and shoot are represented as springing from the same point, and in monocotyledons from opposite poles in the seed. No further effective work was done on the germinating seed until the invention of the microscope, and the appearance of the work of Highmore (1613-85), Much has been written as to the knowledge of the sex of plants among the ancients. It may be stated that of the sexual elements of the flower no ancient writer had any clear idea. Nevertheless, sex is often attributed to plants, and the simile of the Loves of Plants enters into works of the poets. Plants are frequently described as male and female in ancient biological writings also, and Pliny goes so far as to say that some students considered that all herbs and trees were sexual. The comparison of the fertilization of the date palm to the use of the wild fig refers to the practice of Caprification. Theophrastus tells us that there are certain trees, the fig among them, which are apt to shed their fruit prematurely. To remedy this ‘the device adopted is caprification. Gall-insects come out of the wild figs which are hanging there, eat the tops of the cultivated figs, and so make them swell’. Theophrastus was not very successful in distinguishing the nature of the primary elements of plants, though he was able to separate root, stem, leaf, stipule, and flower on morphological as well as to a limited extent on physiological grounds. For the root he adopts the familiar definition, the only one possible before the rise of chemistry, that it ‘is that by which the plant draws up nourishment’, Fig. 8. THEOPHRASTUS From VILLA ALBANI Theophrastus has a perfectly clear idea of plant distribution as dependent on soil and climate, and at times seems to be on the point of passing from a statement of climatic distribution into one of real geographical regions. The general question of plant distribution long remained at, if it did not recede from, the position where he left it. The usefulness of the manuscript and early printed herbals in the West was for centuries marred by the retention of plant descriptions prepared for the Greek East and Latin South, and these works were saved from complete ineffectiveness only by an occasional appeal to nature. With the death of Theophrastus about 287 b. c. pure biological science substantially disappears from the Greek world, and we get the same type of deterioration that is later encountered in other scientific departments. Science ceases to have the motive of the desire to know, and becomes an applied study, subservient to the practical arts. It is an attitude from which in the end applied science itself Celsus, who flourished about 20 b. c., wrote an excellent work on medicine, but gives all too little glimpse of anatomy and physiology. Rufus of Ephesus, however, in the next century practised dissection of apes and other animals. He described the decussation of the optic nerves and the capsule of the crystalline lens, and gave the first clear description that has survived of the structure of the eye. The second Christian century brings us two writers who, while scientifically inconsiderable, acted as the main carriers of such tradition of Greek biology as reached the Middle Ages, Pliny and Dioscorides. Pliny (a. d. 23-79), though a Latin, owes almost everything of value in his encyclopaedia to Greek writings. In his Natural History we have a collection of current views on the nature, origin, and uses of plants and animals such as we might expect from an intelligent, industrious, and honest member of the landed class who was devoid of critical or special scientific skill. Scientifically the work is contemptible, but it demands mention in any study of the legacy of Greece, since it was, for centuries, a main conduit of the ancient teaching and observations on natural history. Read throughout the ages, alike in the darkest as in the more enlightened periods, copied and recopied, translated, commented on, extracted and abridged, a large part of Pliny’s work has gradually passed into folk-keeping, so that through its agency the gipsy fortune-teller of to-day is still reciting garbled versions of the formulae of Aristotle and Hippocrates of two and a half millennia ago. The fate of Dioscorides (flourished a. d. 60) has been not dissimilar. His work On Materia Medica consists of a series of short accounts of plants, arranged almost without reference to the nature of the plants themselves, but quite invaluable for its terse and striking descriptions which often include habits and habitats. Its history has shown it to be one of the most influential botanical treatises ever penned. It provided most of the little botanical knowledge that reached the Middle Ages. It furnished the chief stimulus to botanical research at the time of the Renaissance. It has decided the general form of every modern pharmacopoeia. It has practically determined modern plant nomenclature both popular and scientific. Translated into nearly every language from Anglo-Saxon and ProvenÇal to Persian and Hebrew, appearing both abstracted and in full in innumerable beautifully illuminated manuscripts, some of which are still among the fairest treasures of the great national libraries, Dioscorides, the drug-monger, appealed to scholasticized minds for centuries. The frequency with which fragments of him are encountered in papyri shows how popular his work was in Egypt in the third and fourth centuries. One of the earliest datable Greek codices in existence is a glorious volume of Dioscorides written in capitals, Fifth century drawings from JULIANA ANICIA MS., Fig. 9. Between the foundation of the Alexandrian school and the time of Galen, medicine was divided among a great number of sects. Galen was an eclectic and took portions of his teaching from many of these schools, The basic principle of life, in the Galenic physiology, is a spirit, anima or pneuma, drawn from the general world-soul in the act of respiration. It enters the body through the rough artery (t?a?e?a ??t???a, arteria aspera of mediaeval notation), the organ known to our nomenclature as the trachea. From this trachea the pneuma passes to the lung and then, through the vein-like artery (??t???a f?e?d??, arteria venalis of mediaeval writers, the pulmonary vein of our nomenclature), to the left ventricle. Here it will be best to leave it for a moment and trace the vascular system along a different route. Ingested food, passing down the alimentary tract, was absorbed as chyle from the intestine, collected by the portal vessel, and conveyed by it to the liver. That organ, the site of the innate heat in Galen’s view, had the power of elaborating the chyle into venous blood and of imbuing it with a spirit or pneuma which is innate in all living substance, so long as it remains alive, the natural spirits (p?e?a f?s????, spiritus naturalis of the mediaevals). Charged with this, and also with the nutritive material derived from the food, the venous blood is distributed by the liver through the veins which arise from it in the same way as the arteries from the heart. These veins carry nourishment and natural spirits to all parts of the body. Iecur fons venarum, the liver as the source of the veins, remained through the centuries the watchword of the Galenic physiology. The blood was held to ebb and flow continuously in the veins during life. Fig. 11. Illustrating Galen’s physiological teaching. But among the great arterial vessels that sent forth arterial blood thus charged with vital spirits were certain vessels which ascended to the brain. Before reaching that organ they divided up into minute channels, the rete mirabile (p???a ???st?? ?a?a), and passing into the brain became converted by the action of that organ into a yet higher type of spirits, the animal spirits (p?e?a ???????, spiritus animalis), an ethereal substance distributed to the various parts of the body by the structures known to-day as nerves, but believed then to be hollow channels. The three fundamental faculties (d???e??), the This physiology, we may emphasize, is not derived from an investigation of human anatomy. In the human brain there is no rete mirabile, though such an organ is found in the calf. In the human liver there is no hepatic vein, though such an organ is found in the dog. Dogs, calves, pigs, bears, and, above all, Barbary apes were freely dissected by Galen and were the creatures from which he derived his physiological ideas. Many of Galen’s anatomical and physiological errors are due to his attributing to one creature the structures found in another, a fact that only very gradually dawned on the Renaissance anatomists. The whole knowledge possessed by the world in the department of physiology from the third to the seventeenth century, nearly all the biological conceptions till the thirteenth, and most of the anatomy and much of the botany until the sixteenth century, all the ideas of the physical structure of living things throughout the Middle Ages, were contained in a small number of these works of Galen. The biological works of Aristotle and Theophrastus lingered precariously in a few rare manuscripts in the monasteries of the East; the total output of hundreds of years of Alexandrian and Pergamenian activities was utterly destroyed; the Ionian biological works, of which a sample has by a miracle survived, were forgotten; but these vast, windy, ill-arranged treatises of Galen lingered on. Translated into Latin, Syriac, Arabic, and Hebrew, they saturated the intellectual world of the Middle Ages. Commented on by later Greek writers, who were themselves in turn translated into the same list of languages, they were yet again served up under the names of such Greek writers as Oribasius, Paul of Aegina, or Alexander of Tralles. What is the secret of the vitality of these Galenic biological After Galen there is a thousand years of darkness, and biology ceases to have a history. The mind of the Dark Ages turned towards theology, and such remains of Neoplatonic philosophy as were absorbed into the religious system were little likely to be of aid to the scientific attitude. One department of positive knowledge must of course persist. Men still suffered from the infirmities of the flesh and still sought relief from them. But the books from which that advice was sought had nothing to do with general principles nor with knowledge as such. They were the most wretched of the treatises that still masqueraded under the names of Hippocrates and Galen, mostly mere formularies, antidotaries, or perhaps at best symptom lists. And, when the depression of the western intellect had passed its worst, there was still no biological material on which it could be nourished. The prevailing interest of the barbarian world, at last beginning to settle into its heritage of antiquity, was with Logic. Of Aristotle there survived in Latin dress only the Categories and the De interpretatione, the merciful legacy of Boethius, the last of the The earliest biological treatises that became accessible in the west were rendered not from Greek but from Arabic. The first of them was perhaps the treatise pe?? ??? ????se??, On movement of muscles of Galen, a work which contains more than its title suggests and indeed sets forth much of the Galenic physiological system. It was rendered into Latin from the Arabic of Joannitius (Hunain ibn Ishaq, 809-73), probably about the year 1200, by one Mark of Toledo. It attracted little attention, but very soon after biological works of Aristotle began to become accessible. The first was probably the fragment On plants. The Greek original of this is lost, and besides the Latin, only an Arabic version of a former Arabic translation of a Syriac rendering of a Greek commentary is now known! Such a work appeared from the hand of a translator known as Alfred the Englishman about 1220 or a little later. Neither it nor another work from the same translator, On the motion of the heart, which sought to establish the primacy of that organ on Aristotelian grounds, can be said to contain any of the spirit of the master. Yet the advent of these texts was coincident with a returning desire to observe nature. Albert, with all his scholasticism, was no contemptible naturalist. He may be said to have begun first-hand plant study in modern times so far as literary records are concerned. His book ‘Between the mode of development (anathomiam generationis) of birds’ and fishes’ eggs there is this difference: during the development of the fish the second of the two veins which extend from the heart [as described by Aristotle in birds] does not exist. For we do not find the vein which extends to the outer covering in the eggs of birds which some wrongly call the navel because it carries the blood to the exterior parts; but we do find the vein that corresponds to the yolk vein of birds, for this vein imbibes the nourishment by which the limbs increase.... In fishes as in birds, channels extend from the heart first to the head and the eyes, and first in them appear the great upper parts. As the growth of the young fish increases the albumen decreases, being incorporated into the members of the young fish, and ‘While the young [fish] are small and not yet fully developed they have veins of great length which take the place of the navel-string, but as they grow and develop, these shorten and contract into the body towards the heart, as we have said about birds. The young fish and the eggs are enclosed and in a covering, as are the eggs and young of birds. This covering resembles the dura mater [of the brain], and beneath it is another [corresponding therefore to the pia mater of the brain] which contains the young animal and nothing else.’ In the next century Conrad von Megenberg (1309-98) produced his Book of Nature, a complete work on natural history, the first of the kind in the vernacular, founded on Latin versions, now rendered direct from the Greek, of the Aristotelian and Galenic biological works. It is well ordered and opens with a systematic account of the structure and physiology of man as a type of the animal creation, which is then systematically described and followed by an account of plants. Conrad, though guided by Aristotle, uses his own eyes and ears, and with him and Albert the era of direct observation has begun. But there was another department in which the legacy of Greece found an even earlier appreciation. For centuries the illustrations to herbals and bestiaries had been copied from hand to hand, continuing a During the sixteenth century the energy of botanists and zoologists was largely absorbed in producing most carefully annotated and illustrated editions of Dioscorides and Theophrastus and accounts of animals, habits, and structure that were intended to illustrate the writings of Aristotle, while the anatomists explored the bodies of man and beast to confirm or refute Galen. The great monographs on birds, fishes, and plants of this period, ostensibly little but commentaries on Pliny, Aristotle, and Dioscorides, represent really the first important efforts of modern times at a natural history. They pass naturally into the encyclopaedias of the later sixteenth century, and these into the physiological works of the seventeenth. Aristotle was never a dead hand in Biology as he was in Physics, and this for the reason that he was a great biologist but was not a great physicist. With the advance of the sixteenth century the works of Aristotle, and to a less extent those of Dioscorides and Galen, became the great stimulus to the foundation of a new biological science. Matthioli (1520-77), in his commentary on Dioscorides (first edition 1544), which was one of the first works of its type to appear in the vernacular, made a number of first-hand observations on the habits and structure of plants that is startling even to a modern botanist. About the same time Galenic physiology, expressed also in numerous works in the vulgar tongue and rousing the curiosity of the physicians, became the clear parent of modern physiology and comparative anatomy. But, above all, the Aristotelian biological works were fertilizers of the mind. It is very interesting to watch a fine observer such as Fabricius ab Acquapendente (1537-1619) laying the foundations of modern embryology in a splendid series of first-hand observations, treating his own great researches almost as a commentary on Aristotle. What an impressive contrast to the arid physics of the time based also on Aristotle! ‘My purpose’, says Fabricius, ‘is to treat of the formation of the foetus in every animal, setting out from that which proceeds from the egg: for this ought to take precedence of all other discussion of the subject, both because it is not difficult to make out Aristotle’s view of the matter, and because his treatise on the Formation of the Foetus from the egg is by far the fullest, and the subject is by much the most extensive and difficult.’ The industrious and careful Fabricius, with a wonderful talent for observation lit not by his own lamp but by that of Aristotle, bears a relation to the master much like that held by Aristotle’s pupil in the flesh, Theophrastus. The works of the two men, Fabricius and Theophrastus, bear indeed a resemblance to each other. Both rely on the same group of general ideas, both progress in much the same ordered calm from observation to observation, both have an inspiration which is But Fabricius was more happy in his pupils than Theophrastus, for we may watch the same Aristotelian ideas fermenting in the mind of Fabricius’s successor, the greatest biologist since Aristotle himself, William Harvey (1578-1657). With the second half of the seventeenth century and during a large part of the eighteenth the biological works of Aristotle attracted less attention. The battle against the Aristotelian physics had been fought and won, but with them the biological works of Aristotle unjustly passed into the shadow that overhung all the idols of the Middle Ages. The rediscovery of the Aristotelian biology is a modern thing. The collection of the vast wealth of living forms absorbed the energies of the generations of naturalists from Ray (1627-1705) and Willoughby (1635-72) to RÉaumur (1683-1757) and Linnaeus (1707-1778) and beyond to the nineteenth century. The magnitude and fascination of the work seems almost to have excluded general ideas. With the end of this period and | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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