Leonardo da Vinci - the anatomist (1930) 20
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McMurrich JP. Leonardo da Vinci - the anatomist. (1930) Carnegie institution of Washington, Williams & Wilkins Company, Baltimore.
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Leonardo da Vinci - The Anatomist
Chapter XX Comparative Anatomy
It was the anatomy of the human body that especially interested Leonardo. Approaching it from the standpoint of an artist, he became more and more absorbed in its details until he came to study it as an anatomist, striving to obtain a correct idea of the structure and relations of the parts of the body that he might better understand their mode of action. In default of human material he did not disdain, however, the study of the parts of animals, and a number of his notes and drawings are evidently based upon animal dissections. Attention has already been drawn to some of these cases, as when he describes as if it were human the heart of the ox with its os cordis and welldeveloped moderator band, the larynx and hyoid bone of, probably, a dog, the brain of an ox with its rete mirabile, the mode of origin of the great vessels from the aortic arch in the ox, the placental cotyledons of a calf.
Leonardo fell into the same mistake as did Galen and the Salernitans in supposing that he could get an accurate idea of human structures by the study of those of animals. Thus he asserts that all terrestrial animals have similitudes of members, such as muscles, nerves and bones, the only differences being in length or width, as will be shown in the Notomia. In aquatic animals, however, there is great variety, so that a type for them can not be established; and so too it is with insects (G, 5v). But he also was aware that in many cases animal structures differed from human and there are many notes suggesting the dissection of animal forms, partly out of curiosity to learn in w T hat they differed from man, partly, one may believe, in the hope that a study of their differences might throw light upon their form and function in Man. Thus on AnB, 9v are sketches of the arm skeleton and biceps muscle of a man and an ape, and it is pointed out that the nearer the insertion of the muscle is to the hand, the greater the weight that may be raised by it, “and this makes the ape more powerful in its arms than is man, according to its proportions.” It must be confessed, however, that there is no evidence that he carried out many of his proposed comparative studies. Indeed, the scope of his suggestions was too wide to be covered by one who had as many interests as Leonardo; but, nevertheless, while one can not, with Bottazzi (1910), regard him as the founder of the comparative analytical method of anatomy, for that was the method pursued by Aristotle, he was, before Pierre Belon (1555) the reviver of that method after it had lain fallow for many centuries.
Fig. 88. Dissection of the foot of a bear. (QV, 11.)
Leonardo clearly perceived the anatomical similarity of man to the lower animals, speaking of him as “prima bestia infralli animali” (An A, 1), and in an interesting sketch of the classification of familiar mammals he groups man with (1) “those that are almost of similar species, and as the baboon, the monkey and the like, which are many.” His other groups are (2) lions and their like, as panthers, lionesses, leopards (cats), lynxes, Spanish cats (?), genets and common cats; (3) horses and their like, as the mule, ass and the like that have teeth both above and below; (4) bulls and their like, that have horns and are without teeth above, as the buffalo, stag, fallow deer, roe-deer, sheep, goat, ibex, mucheri (?), chamois, giraffe (AnB, 13). One wonders whether Leonardo’s generalization as to the teeth and horns of the Ungulate groups was based on his own observations or was a reminiscence from Aristotle’s De partibus, perhaps through Albertus Magnus.
He makes a memorandum to discuss the similarities that the bones and muscles of animals have to those of man (QV, 22) and he has left a sketch of the carpus and hand of a monkey ( scimmia ) (QV, 21 v). In the outline of a mode in which he hoped to discuss and figure in his proposed treatise the anatomy of the lower limb (An A, 17) one reads — “Figure here the foot of a bear and monkey and other animals, as to how tney differ from the foot of man. And also represent the feet of some birds.”
It has been seen that he had made dissections of a monkey and, probably, four beautiful drawings in silver-point (QV, 11 to 14) (fig. 88) represent dissections of the foot of a bear, there being further evidence in a remark concerning the tendons of its fore-paw that he had made a dissection of that animal (QI, 2).
So too one must conclude that he had studied the brain and nasal cavity of the lion. Speaking of his belief that the senses of man are more obtuse and grosser than those of animals, he refers this condition to man’s sense-organs being less ingenious and less capable of receiving the sensory virtue. For he found that in the lion for the sense of smell the brain sent portions of its substance into a rather capacious receptacle, divided into a large number of cartilaginous saccules, between which were sufficient passageways to allow the stimulus to reach the brain; evidently a description of the highly developed nasal conchse of a carnivore. And furthermore he notes that the orbits of the lion occupy a large part of the head and its optic nerve joins the brain quickly, whereas in man the orbits are relatively small and the optic nerves are slender, long and weak (AnB, 13 v). Of the dog, in addition to the probability that the larynx and hyoid bone figured on QV, 16, 17 (fig. 66) is that of a dog, he has a memorandum to study its lumbar region, the diaphragm and the motions of the ribs. Further, on QI, 96 there is a sketch showing certain proportions of a dog’s head, but these are more interesting from an artistic than from a scientific standpoint.
Leonardo makes no statements as to the sources from which he obtained the material for his comparative studies. It may be conjectured that some of the animals mentioned, such as monkeys, were kept as pets by members of the ducal courts, while others may have been made available as the results of hunting expeditions. In the case of the lions, the Florentine Diary of Luca Landucci (1450-1516) gives the information that accordng to ancient custom lions were kept in cages behind the Palazzo del Capitano, later incorporated in the Palazzo Vecchio. The custom was discontinued toward the end of the seventeenth century, but the street on which the cages fronted is still known as Via de Leoni.
Among other suggestions of comparative studies may be mentioned a comparison of the intestines of man with those of the monkey, the lion group, the ox and birds — a special discourse to be made of these investigations (AnB, 37). He notes that animals •without feet have a straight intestine, since they are always prone; but in man, on account of his erect position, the stomach would immediately empty itself were it not for the coiling of the intestines, which aids in digestion and absorption (AnB, 14v). He planned the dissection of the eye of various animals to discover the muscles that open and close the pupil (G, 44); the study of the facial muscles and their innervation in the horse, because in that animal they are large and very evident (AnA, 13v); the tongue of the wood-pecker is suggested as an object for study (QI, 13; QIV, 10), as is also the jaw of the crocodile (QI, 13), probably in connection with the ancient belief that the crocodile was the only animal in which the upper jaw was movable. The leg of the frog was to be figured for comparison with that of man, for it was supposed to be very similar both as regards the bones and the muscles, and with this there was to be a representation of the hind-legs of the hare, which are very muscular and with speedy muscles, because they are not impeded with fat (QV, 23). Nor did he confine his investigations to the vertebrate group of animals, invertebrates, though rarely, also claiming his attention.
“That the flies have their voice in the wings you will see by cutting them a little or, better still, by anointing them a little with honey, so that they are not altogether hindered from flying. And you will see that the sound made by the movement of the wings is made raucous, and so much the more will the voice change from high to low, the more their wings are hindered.” (AnA, 15v.)
Fie also refers (K, 81) to the old legend which regarded the Gordian worms, occasionally to be found in fresh-water streams or pools and still popularly known as hair worms, as the hairs of cattle that had fallen into the water and acquired the power of twisting and writhing as if endowed with life.
Leonardo’s experimental study on the central nervous system of the frog and his observations on the development of the chick and on the fetal membranes of the cow have already been mentioned in Chapters XVII and XIX and need not be further considered here. But just as his desire to depict accurately the human form stimulated him to the study of human anatomy, so also two other interests led him to special studies of the anatomy of the horse and of that of birds, but in neither case were his investigations carried so far as were those in human anatomy.
The founder of the fortunes of the Sforze was the Condottiere Muzio Attendolo, who, from his great strength, was nicknamed Sforza, and who became commander-in-chief of the Neapolitan forces under Queen Joanna II. His son, Franceseo, married Bianca Maria Visconti, natural daughter of the Duke of Milan, and, on the death of her father without heirs (1466), Francesco succeeded to the Duchy, establishing the short-lived dynasty of the Sforze. As early as 1473 Francesco’s son, Galeazzo Maria, had conceived the idea of perpetuating his father’s memory by the erection of a bronze equestrian statue, but the political exigencies of the times prevented the fulfillment of his intentions before his death in 1476. The Duchy then passed into the hands of Gian Galeazzo, a mere child, for whom his uncle Ludovico acted as regent, succeeding to the Duchy on the death, whether naturally or by design, of his nephew. Once established in power, Ludovico revived his brother’s idea of a statue of Francesco, and, according to Solmi’s account (1919) applied to Lorenzo di Medici for advice as to a competent artist. Leonardo was recommended, and in his remarkable letter to Ludovico, offering his services, one of the items which he states he is prepared to undertake is this equestrian statue.
“Also” he wrote, “I can undertake the work on the Horse, which will be to the immortal glory and eternal honor of the happy memory of my lord your father and of the illustrious house of Sforza.”
Leonardo went to Milan in 1483, but it was not until ten years later that a colossal plaster model of the horse was set up in the grand square before the Gastello. It may well be supposed that during these years Leonardo was, amidst other things, perfecting his knowledge of the surface anatomy and proportions of the horse, by the same methods as those he had used earlier in the study of the human body. But in the case of the horse his studies were almost entirely from the artistic standpoint; he did not carry them to a thorough investigation of the various parts and organs. It was the artist rather than the scientist that was at work.
The majority of the sketches of the horse are in the Windsor collection and have been reproduced in the Rouveyre edition of the Windsor folios, forming volume 15 of that edition, with reproductions of no less than 67 folios. The title given to this volume is A T otes et croquis sur Vanatomie du cheval and it awakens expectations of much of anatomical interest. The figures, however, are largely postural studies or notes on proportions, or, at best, sketches of the surface anatomy of the limbs. Scattered through the other collections there are, however, a few figures that compare certain of the thigh muscles of the horse with those of man. Thus on QV, 22 (fig. 12) there is a drawing of the skeleton of the hind-leg of a horse placed alongside one of the skeleton of a human leg, certain of the muscles descending from the pelvis, such as the rectus, the tensor fasciae latae, the adductor magnus and the glutei being represented in each by bands or cords. Accompanying the figures are various memoranda, one to the effect that, to insure more exact comparison, the knee of the man should be figured bent as is that of the horse, another noting that for the same purpose the man should be represented as standing on tip-toes. Somewhat similar figures are to be found on AnB, I, and on K, 102 and 109.
The figures illustrating the proportions of the horse’s body have but little scientific interest, nor are they sufficiently definite to allow of the establishment of a canon of proportion. They are mostly sketches with lines drawn across them, labeled with numbers or letters indicating the dimensions of the part. Thus, to take an example from elsewhere than the Windsor collection, there is on A, 62 a sketch of a horse’s head enclosed within an oblong, which is divided into three parts by transverse lines. There are no labels in this case, but accompanying memoranda give the following data. From the base of one ear to the other equals the interval from the eyebrows to the chin (i.e. the angle of the mandible) ; the size of the mouth equals from the division of the lips below r the chin (not quite clear) ; from one ear to the other is equal to the length of the ear; the length of the ear is one-quarter the length of the face. The author of the preface to Rouveyre’s A T otes et Croquis, Colonel Duhousset, believes that Leonardo took as his canon of proportion for the horse the length of the head and indicated it on his sketches by the Symbol T, the measurement of the neck at the withers for instance being labeled I T and the distance of the hock from the ground T I. The sketch and memoranda mentioned above may be taken as supporting the contention that the length of the head was adopted as a canon, but there are others from which it is difficult to ascertain that any definite standard for comparison had been selected. A prolonged discussion of the question would be out of place here, seeing, as has already been stated, that the studies, so far as Leonardo was concerned, were of purely artistic interest and had not been carried out sufficiently to have become of scientific value.
The second interest that led Leonardo into special comparative anatomical studies was his desire to invent a flying machine. He claimed to have already invented a submarine, whose construction he refrains from revealing on account of its enormous possibilities for destruction, and his inventive genius stimulated him to the further conquest of the air. It was, of course, a heavier-than-air machine that he had in view, and he turned to the bird, the most perfect of all such machines, to discover the principles that governed its flight. It was natural that he should do so; that was his method, the modern method — in attacking any problem to seek an understanding of the fundamental principles that lay behind it. And so he proceeded to study the flight of birds, their soaring, hovering and swooping, their manner of changing direction and of adapting themselves to varying wind currents, the differences in the flight of kites, sparrows and thrushes, differences in the movement of the wings of magpies, doves and rooks, the use of the tail as a rudder and control. And it is surprising how much he was able to discover by keen observation, without such modern aids as instantaneous photography. He had it in mind to write a treatise on these topics.
“I have divided,” he says, “the Treatise on Birds into four books; the first of which treats of their flight by beating their wings; the second of flight without beating the wings and with the help of the wflnd; the third of flight in general, such as that of birds, bats, fishes, animals and insects; the last of the mechanism of this movement.” (K, 3.)
But, as was the case with the Anatomy, this intention was never fulfilled, though many notes dealing with the topics ment ioned are to be found scattered through the Codex Atlanticus, the Windsor folios and the volumes in the Institut de France (especially E, K and L) and, furthermore, there is a small volume of thirty pages, with sketches and notes written a rebours, almost entirely pertaining to the flight of birds. This last has been published in facsimile by Sabachnikoff, with transcription and notes by Piumati, under the title Codice sul volo degli Ucelli e varie altre materie (Paris, Rouveyre, 1893) (see p. 68).
The moving idea that led to the observations recorded in these memoranda was the possibility of the construction of a machine by which man would be able to navigate the air like a bird. It was, accordingly, a problem in mechanics with which Leonardo was confronted and questions of anatomical structure were of subordinate interest. There is therefore, little that need be discussed here in connection with the studies on birds; merely one or two points of anatomical interest need be considered. As to the mechanics of flight it will suffice to say that Leonardo had discovered their essential principles; but there was lacking then and until comparatively recent times a suitable source of motive power to give these principles practical effect.
“A bird” he says “is a machine working according to mathematical law, which machine it is within the capability of man to reproduce with all its movements, but not with a corresponding degree of strength.” (C. A. 161.)
As Beltrami (1910) has pointed out Leonardo had understood that —
“Weight, instead of being an obstacle, was an essential condition of flight and that the bird can fly because, being heavier than air, it does not remain in the power of this, but succeeds in profiting by the resistance which this very weight can oppose to it.”
There are, however, three points of anatomical import that may be briefly mentioned. On QIV, Iv there is an admirable study of a bird’s wing (fig. 89) showing the bones, the attachment of the feathers and certain tendons. It is a study of the behavior of the feathers during the action of the wing in flight, an accompanying memorandum indicating that one of the tendons shown acts on the feathers in such a way as to draw their tips “toward the elbow of the wing” when the wing is being folded, but when it is extended by another tendon “the feathers direct their length toward the tip of the wing.”
The great development of the pectoral muscles of birds is noted, the statement being that they are heavier than all the rest of the body (AnA, 12v), but in the Codice sul volo dei Uccelli it is argued that the excessive development of these muscles is not necessary for flight — comparatively little power is necessary to sustain the bird in the air, but the extra power is furnished to give rapid motion, so that enemies may be avoided or prey secured, and, further, to allow the bird to carry heavy burdens in its talons, as when a falcon carries a duck or an eagle a hare. These exigencies made needful the doubling or trebling of the power required for flight and explain not only the large pectoral muscles, but also the one-piece breast bone, the wings —
“all interwoven with large sinews ( [nervi ) and other very powerful ligaments of cartilage and the very strong skin with various muscles.” (Sa., 16.)
Leonardo was probably the first to describe the so-called bastard wing or alula, that portion of the wing whose feathers are attached to the pollex of the bird’s hand and may, therefore, have some independent movement. He speaks of the pollex as il dito grosso and regards it as that part of the wing that meets with the greatest resistance from the air and is therefore strong, provided with very strong tendons and short feathers of greater strength than those of any other part of the wing. It is that part of the wing that especially propels the bird forward, and in this respect he compares it to the claws of a cat climbing a tree, although he also speaks of it as a rudder, just as is the tail (Sa, 14v). The manner in which his rudder acts is described on K, 7v, but the passage is not of anatomical interest.
Fig. 89. Dissection of a bird’s wing. (QIV, 1.)
But after all Leonardo saw clearly that his flying machine could not be constructed on the plan of the bird with feathers.
“Remember” he says “that thy bird should not imitate anything else than the bat, since its membranes make an armature or a building together of the armatures, that is to say of the framework of the wings. And if you imitate the wings of the feathered birds, these are much more bone and sinew ( nerva turn), since they are penetrable, that is to say, their feathers are separate and the air may pass between them. But the bat is aided by its membrane that binds the whole and is not penetrable.” (Sa, 16.)
F urther there is a memorandum to dissect a bat, study it carefully and on this model to construct the flying-machine, but there is no evidence that such a dissection was made (F. 41v).
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Reference: McMurrich JP. Leonardo da Vinci - the anatomist. (1930) Carnegie institution of Washington, Williams & Wilkins Company, Baltimore.
Cite this page: Hill, M.A. (2020, July 13) Embryology Leonardo da Vinci - the anatomist (1930) 20. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Leonardo_da_Vinci_-_the_anatomist_(1930)_20
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