Charles McRae

“ It was not until after Vesalius had been three years professor that he began to distrust the infallibility of Galen's anatomical teaching. Constant practical experience in dissection, both human and comparative, slowly convinced him that—great anatomist as the "divus homo" had undoubtedly been—his statements were not only incomplete, but often wrong; further, that Galen very rarely wrote from actual inspection of the human subject, but based his teaching on a belief that the structure of a monkey was exactly similar to that of a man. ”

“ The importance of Harvey's discovery of the circulation of the blood can only be properly estimated by bearing in mind what was done by his predecessors in the same field of inquiry. Aristotle had taught that in man and in the higher brutes the blood was elaborated from the food in the liver, conveyed to the heart, and thence distributed by it through the veins to the whole body. Erasistratus and Herophilus held that, while the veins carried blood from the heart to the members, the arteries carried a subtle kind of air or spirit. ”

“ The theory of Epigenesis, which makes the embryo arise, by a series of successive differentiations, from a simple homogeneous mass into a complex heterogeneous organism.
The above quotation will show how closely Aristotle held to the theory of Epigenesis; and in another place he says, "Not at once is the animal a man or a horse, for the end is last attained; and the specific form is the end of each development."
Spontaneous generation is nowadays rejected by science; but Aristotle went so far as to believe that insects, molluscs, and even eels, were spontaneously generated. ”

“ But Aristotle did not consider the "pneuma," which thus reached the interior of the blood-vessels, to be exactly the same thing as air—it was "a subtilized and condensed air." [11] And this we now know to be oxygen.
The treatise "On the Generation of Animals" is an extraordinary production. "No ancient and few modern works equal it in comprehensiveness of detail and profound speculative insight. We here find some of the obscurest problems of biology treated with a mastery which, when we consider the condition of science at that day, is truly astounding. ”

“ The brain tempers the heat and seething of the heart.... In order that it may not itself be absolutely without heat, blood-vessels from the aorta end in the membrane which surrounds the brain.... Of all animals man has the largest brain in proportion to his size: and it is larger in men than in women. This is because the region of the heart and of the lung is hotter and richer [34] in blood in man than in any other animal; and in men than in women. This again explains why man alone of animals stands erect. ”

“ Although the heart is not really the first part to appear, the observation of its very early appearance in the embryo, which he treats more fully elsewhere, [8] is alone enough to establish his reputation as an original observer. It is remarkable that Aristotle should have overlooked the presence of the valves of the heart, the structure and functions of which were fully investigated within thirty years of his death by the anatomists of the Alexandrian school. ”

“ Aristotle discusses and rejects the theory that the male reproductive element is derived from every part of the body. He concludes that "instead of saying that it comes from all parts of the body, we should say that it goes to them. It is not the nutrient fluid, but that which is left over, which is secreted. Hence the larger animals have fewer young than the smaller, for by them the consumption of nutrient material will be larger and the secretion less. ”

“ It will be observed that here Aristotle so correctly describes the position of the human heart as to render it probable that he is speaking from actual inspection; although man is not the only animal in which the heart is turned towards the left. In contrasting the heart with the other viscera he appears to have overlooked the existence of the coronary vessels, and to have imagined that the nutrition of the heart was effected directly by the blood in its cavities. ”

“ Some follow a leader, others act independently. Various differences are in this way pointed out, and there is no lack of illustration and detail, but a suspicion is excited that the generalizations are sometimes based upon insufficient facts. The book closes with a description of the different parts of the human body, both internal and external. In speaking of the ear, Aristotle seems to have been aware of what we now call the Eustachian tube, for he says, "There is no passage from the ear into the brain, but there is to the roof of the mouth." ”

“ The heart is the first of all the parts of the body to be formed, and no sooner is it formed than it contains blood.... For no sooner is the embryo formed than its heart is seen in motion like a living creature, and this before any of the other parts. The heart is abundantly supplied with sinews.... In no animal does the heart contain a bone, certainly in none of those that we ourselves have inspected, with the exception of the horse and a certain kind of ox. In animals of great size the heart has three cavities; in smaller animals it has two ”

“ The philosopher seems to have been a favourite with both the king and the prince, and, in gratitude for his services, Philip rebuilt Stagira and restored it to its former inhabitants, who had either been dispersed or carried into slavery. The king is said also to have established there a school for Aristotle. The high respect in which Alexander held his teacher is expressed in his saying that he honoured him no less than his own father, for while to one he owed life, to the other he owed all that made life valuable. ”

“ Biology was in so early a stage that a theory had often of necessity to be founded on a very slight basis of facts. Yet, notwithstanding this drawback, so great was the sagacity of this philosopher, that many of his generalizations, which he himself probably looked upon as temporary, have held their ground for twenty centuries, or, having been lost sight of, have been discovered and put forward as original by modern biologists. Thus "the advantage of physiological division of labour was first set forth," says Milne-Edwards, "by myself in 1827;" ”

“ With regard to the second class of causes producing diseases, he attributed many disorders to a vicious system of diet, for excessive and defective diet he considered to be equally injurious.
In his medical doctrines Hippocrates starts with the axiom that the body is composed of the four elements—air, earth, fire, and water. From these the four fluids or humours (namely, blood, phlegm, yellow bile, and black bile) are formed. Health is the result of a right condition and proper proportion of these humours, disease being due to changes in their quality or distribution. ”

“ His descriptions of the vertebræ, with all their processes and ligaments, as well as his account of the general characters of the internal viscera, would not have been as free from error as they are if he had derived all his knowledge from the dissection of the inferior animals. Moreover, it is indisputable that, within less than a hundred years from the death of Hippocrates, the human body was openly dissected in the schools of Alexandria—nay, further, that even the vivisection of condemned criminals was not uncommon. ”

“ Following Aristotle especially, he regarded hair, nails, arteries, veins, cartilage, bone, ligament, membranes, glands, fat, and muscle as the simplest constituents of the body, formed immediately from the blood, and perfectly homogeneous in character. The organic members, e.g. lungs, liver, etc., he looked upon as formed of several of the foregoing simple parts. ”

“ His theory of respiration, as explained in his treatise on the subject, is that it tempers the excessive heat produced in the heart. The lung is compared to a pair of bellows. When the lung is expanded, air rushes in; when it is contracted, the air is expelled. The heat from the heart causes the lung to expand—cold air rushes in, the heat is reduced, the lung collapses, and the air is expelled. The cold air drawn into the lung reaches the bronchial tubes, and as the vessels containing hot blood run alongside these tubes, [38] the air cools it and carries off its superfluous heat. ”

“ Of Harvey's scholarship and culture we are not left in ignorance. Bishop Pearson, writing about seven years after the doctor's death, and Aubrey [21] have told us of his appreciation of the works of Aristotle, and in his own writings he refers more frequently to the Stagirite than to any other individual. Sir William Temple [22] has also put it on record that the famous Dr. Harvey was a great admirer of Virgil, whose works were frequently in his hands. His store of individual knowledge must have been great; and he seems never to have flagged in his anxiety to learn more. ”

“ The fact of the brain substance being insensible to mechanical irritation was known to Aristotle, and may have been learnt from the practice of Hippocrates. [35] Lastly, it should be remembered that—though this may have been but a lucky guess on Aristotle's part—the relative weight of brain to the entire body has been shown, with few exceptions, to be greater in man than in any other animal. ”

“ As examples of Aristotle's method of treatment, his descriptions of blood, the brain, the heart, and the lung may be considered.
Of the blood he says, "What are called fibres are found in the blood of some animals, but not of all. There are none, for instance, in the blood of deer and [32] of roes, and for this reason the blood of such animals as these never coagulates.... Too great an excess of water makes animals timorous.... Such animals, on the other hand, as have thick and abundant fibres in their blood are of a more choleric temperament, and liable to bursts of passion.... ”

“ Andreas Vesalius was born at Brussels, on the last day of the year 1514, of a family which for several generations had been eminent for medical attainments. He was sent as a boy to Louvain, where he spent the greater part of his leisure in researches into the mechanism of the lower animals. He was a born dissector, who, after careful examination, in his early days, of rats, moles, dogs, cats, monkeys, and the like, came, in after-life, to be dissatisfied with any less knowledge of the anatomy of man. ”

“ The importance attached by the Asclepiads to the habit of physical observation, which has been already referred to in the life of Hippocrates, secured for Aristotle, from his earliest years, that familiarity with biological studies which is so clearly evident in many of his works.
Both parents of Aristotle died when their son was still a youth, and in consequence of this he went to reside with Proxenus, a native of Atarneus, who had settled at Stagira. Subsequently he went to Athens and joined the school of Plato. ”

“ He maintained that the nerves of the finer senses are formed of matter too soft to be the vehicles of muscular motion; whereas, on the other hand, the nerves of motion are too hard to be susceptible of fine sensibility. His description of the method of demonstrating the different parts of the brain by dissection is very interesting, and, like his references to various instruments and contrivances, proves him to have been a practical and experienced anatomist. ”

“ It is difficult to speak of the skill and painstaking perseverance of Hippocrates in terms which shall not [16] appear exaggerated and extravagant. His method of cultivating medicine was in the true spirit of the inductive philosophy. His descriptions were all derived from careful observation of its phenomena, and, as a result, the greater number of his deductions have stood unscathed the test of twenty centuries. ”

“ This was done by Malpighi in 1661, who saw in the lung of a frog, which was so mounted in a frame as to be viewed by transmitted light, the network of capillaries which connect the last ramifications of the arteries with the radicles of the veins.
Harvey rightly denied that the arteries possessed any pulsific power of their own, and maintained that their pulse is owing solely to the sudden distension of their walls by the blood thrown into them at each contraction of the ventricles. ”

“ Some of the air which enters the lung gets from the bronchial tubes into the blood-vessels by transudation, for there is no direct communication between them; and this air, penetrating the body, rapidly cools the blood throughout the vessels. ”

“ When two persons go out to capture them, one shows himself, and either plays upon a pipe or sings, and the other strikes behind, when the first gives him the signal." "Swans have the power of song, especially when near the end of their life; for they then fly out to sea, and some persons sailing near the coast of Libya have met many of them in the sea singing a mournful song, and have afterwards seen some of them die." "Of all wild animals, the elephant is the most tame and gentle; for many of them are capable of instruction and intelligence, and they have been taught to worship the king." ”