Leonardo da Vinci - the anatomist (1930) 13
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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 XIII The Blood-Vessels
Leonardo’s treatment of the blood-vessels is less satisfactory than that of some other portions of his Anatomy, partly on account of its incompleteness, partly because the fact that it was largely based on animal dissections is so much more obvious than it was even in the case of the heart, and partly because the acceptance of certain mythical traditions stand out more egregiously than elsewhere. It seems probable that the representations given of the great vessels date back to the earlier periods of his studies and, from the lack of later illustrations, there are no means for determining how far he may have eventually progressed toward an accurate knowledge of human vascular anatomy.
It is significant that Leonardo uses the term vena with some indefiniteness. Sometimes it clearly means “vein,” at other times it just as evidently means “blood-vessel.” It was not that he did not distinguish between arteries and veins; the difference in their contents was a fundamental part of his theory of the heart’s action and he also accepted Galen’s teaching that the walls of the arteries consisted of two coats and those of the veins of but one (QII, 2v). The indefiniteness came rather from the lack in his day of an appreciation of the necessity for an exact nomenclature, an appreciation that was slow to develop in Anatomy. But while he followed Galen in this particular he departed from his teaching and that of his follower, Avicenna, in another point of some importance. Galen claimed that while the arteries arose from the heart, the veins had their origin in the liver, an idea in harmony with his theory that the nutritive blood was formed in that organ. Leonardo, however, while accepting Galen’s views as to the origin of the blood, states positively that “all the veins and arteries arise from the heart” (AnB, 11) and again that “the root of all the veins is in the gibbous part of the heart” (AnB, 34v), and finds reason for this belief in the fact that the veins and arteries are largest where they join the heart, “and the more they separate from the heart the more they diminish in size and divide into smaller branches” (AnB, 11). He then proceeds to discuss the idea that the veins arise from the branches in the liver just as a plant arises from its rootlet, pointing out that plants do not have their origin from the roots, but these and the other branches, i.e. the radicle and plumule, have their origin from that part of the plant which is situated between the air and the earth. He illustrates this by two figures (fig. 50), one of which represents a nut from which a plumule and radicle are sprouting, while in the other the heart takes the place of the nut and the ascending and descending parts of the vein correspond to the plumule and radicle.
“The heart is the nut which gives rise to the tree of the veins.” (AnB, 11.)
The casting aside of Galen’s theory was an important step, not only because it was a revolt against accepted authority, but also because it meant progress toward a more correct understanding of the heart’s action. As a matter of fact, Aristotle, long before Galen’s time, had maintained that both arteries and veins arose from the heart, and it is interesting to note that another idea which suggests Aristotelian influence occurs in Leonardo’s memoranda. Aristotle describes the wmlls of the aorta as being tendinous, in contrast with those of the veins, which were membranous, and claimed that its ultimate branches were neura (tendons) and consequently were solid and impervious. Leonardo expressed the same idea with the words —
“The artery, by being doubled with nervosita in many places, performs the office of simple nervi (tendons).” (QIII, lOv.)
There is much similarity between this statement and Aristotle’s, but hardly enough to warrant the conclusion that Leonardo was familiar with Aristotle’s anatomical treatises, in the face of the fact that he makes no mention of them (see p. 29) and that his reliance is so definitely on the Galenic tradition.
His comparison of the veins to a sprouting seed has already been mentioned. Much more attractive to him was the comparison of the blood to the ocean and rivers and of the microcosm to the macrocosm, and one finds it made more than once in the various manuscripts.
“As man has within him a pool of blood wherein the lungs as he breathes expand and contract, so the body of the earth has its ocean, which also rises and falls every six hours with the breathing of the world; as from the said pool of blood proceed the veins that spread their branches throughout the human body, so also the ocean fills the body of the earth with an infinite number of veins of water.” (A, 55v.)
One finds the same comparison in Leic, 34 (see p. 97) and again in CA, 171 (seep. 179), while in AnA, 4 it is pointed out that in reality —
“The origin of the sea is the reverse of that of the blood, for the sea receives into itself all the rivers, which are produced only by the aqueous vapor raised into the air; but the sea of blood is the cause of all the veins.”
This last passage is of special interest in that Hopstock (1919) to whom we are so deeply indebted for the Quaderni, quotes it as partial evidence for his belief that Leonardo came very near to the conception of the circulation of the blood. One might say the same of Erasistratus, but the question as to how far, if at all, Leonardo had envisaged a circulation of the blood in the modern sense will be better considered later (p. 177).
Some general statements concerning the blood-vessels may be briefly mentioned. On AnB, 1, it is stated that the function of the veins is to convey heat to the body; veins in this case probably means bloodvessels, for they are contrasted with nerves whose function is to give sensation. On AnB, 10 it is noted that veins and nerves follow the same pathways and that they pass with the arteries from muscle to muscle and ramify in the muscles with equal branchings, but on QIY, 8 he notes as exceptions to this rule that in the arms and legs the veins are superficial and do not accompany the arteries, making a memorandum to discover where they leave the arteries. Two varieties of branching occur in the veins, the simple variety in which the branching goes on indefinitely and the compound in which two branches anastomose to form a single vein. As an example of a compound branching he refers to two branches from the superficial epigastric veins uniting to form the single superficial v. dorsalis penis, a rather unusual course for the single vein.
Though not a physician, Leonardo was interested in pathological conditions, especially such as seemed to promise light upon the causes of the cessation of life. Mention has already been made (p. 53) of a dissection that he made in Florence of the body of an aged man who claimed to be a centenarian; he hoped from the dissection to discover the cause of his easy death and believed that he had found it in the condition of certain vessels. He observed that the splenic artery was tortuous, contracted, wrinkled and empty of blood, whereas in youth it was straight and full of blood (AnB, 22) and attributed this condition to a thickening of the walls of the vessels, so that the blood can not pass through their smaller branches, and so the liver, the heart and the great veins are deprived of blood and all the body of its nourishment (fig. 51). The effect on the liver is especially noted; it loses its color and becomes highly friable, so that by rubbing or washing its substance breaks up into fine particles like sawdust, leaving the branches of the veins intact (AnB, lOv). The cause of death, then, was lack of nourishment caused by a thickening of the walls of the vessels (AnB, lOv) and this thickening is explained by the principle that that augments most which is nearest to the source of nutrition and, since the vessels are envelopes of the blood and this is the source of nutrition for all the body, their walls in time will thicken (AnB, llv).
Leonardo evidently had under observation the condition now termed arterio-sclerosis; he docs not, however, mention calcification of the contorted vessels, but in the same subject he observed in the veins that pass beneath the clavicle calcifications ( pietre ) that were as large as chestnuts, were of the color and form of truffles and were contained in pouches attached to the veins, like goiters (AnB, lOv). He also records that he saw an accidental wound of the vena communis to which a tight bandage was immediately applied and in a few days there developed a large swelling, the size of a goose-egg and full of blood, and it remained for many years (AnB, 10). He mentions this as evidence of the great distensibility of the veins ; it was probably, however, a haematoma, rather than a venous aneurism.
Fig. 51. Superficial veins of arm and a sketch comparing the teries of a centenarian with those of a child. (AnB, 10.)
Fig. 52. Early study of the heart and blood-vessels. (QV, 1.)
Leonardo has left ten drawings representing the great vessels and all, with one exception, give evidence that they were based on animal rather than human dissections and, furthermore, it is probable that several of them, indeed the majority, date from the earlier period of his studies, since in those in which the heart also is shown (QI, 12; QIII, 3, lOv; QIV, 7; and QV, 1) its atria are altogether omitted (figs. 52, 53), except on QIV, 7, where the left one is sketchily shown. This would seem to indicate that these figures were drawn before Leonardo had formulated his flux and reflux theory and had realized the importance of the atria.
That the great majority of these figures are based on animal dissection is shown most clearly by the arrangement of the arteries arising from the aortic arch. The aorta arising from the left ventricle is shown passing directly upward for a short distance and then it divides into two branches, one of which curves to the left and then downward and is evidently the arch of the aorta, while the other continues the upward course but quickly divides into the two common carotids and the two subclavians. This is the arrangement shown on AnB, 11 (fig. 50), in one of the figures on QIII, lOv, and on QIV, 9v, while on QI, 12, and QIV, 7, it is essentially the same except that the right subclavian is not shown. It is the ungulate arrangement, not the human. What Leonardo saw in the dissection of an ungulate he represented correctly; he erred, however, in assuming that the human arrangement was the same and in representing the ungulate arrangement in a human body (QI, 12; QV, 1). In extenuation of the error it may be observed that he had the support of Avicenna, for that author described the origin of the branches of the aortic arch just as Leonardo represents them on the folios mentioned and makes no suggestion that Galen’s description, on which he based his, was made from animal dissections. When Leonardo had opportunity to see these vessels in a human body, as he did in the dissection of il vecchio (p. 53), he represents (fig. 54) their origins as they are in human beings, and a figure on QIII, lOv (fig. 53), in which the left subclavian arises directly from the aortic arch, may possibly have also been drawn from a human preparation, though in some respects it possesses suggestions of the ungulate type.
In his representations of the great veins, Leonardo agains relies on what he found in animal dissections, interpreting his findings in the light of Avicenna’s description. Thus Avicenna describes the vena cava as arising from the gibbosity of the liver and dividing into an ascending and a descending branch (c/. fig. 53). The former when it reaches the level of the heart divides again, one of the branches opening into the right ventricle, the opening being guarded by the valves. This branch is evidently the right atrium and the valves the tricuspid; for Galen, whom Avicenna followed, relying on animal dissections, regarded the inferior and superior vense cavae as continuous and the right atrium as a branch of this main stem. Having thus brought the vena cava into relation with the right ventricle, Avicenna confuses with it the pulmonary artery (vena arterialis ) and so does Leonardo, representing a branch of the vena cava passing directly to the right lung. Furthermore, if the right atrium were regarded as merely a branch of the vena cava, it is natural that Avicenna would describe the coronary sinus of the heart also as a branch of that vessel, and in this too he is followed by Leonardo (QII, 4), who furthermore assigns the origin of the right coronary artery to the pulmonary artery (vena arterialis), although he represents both it and the left coronary as arising from the aorta in QII, 3v. The statement on QII, 4 is probably a lapsus calami. A third branch of the vena cava in the heart region is described by Avicenna as passing downward to the upper thoracic vertebrae. This is what is now know as the azygos vein and is shown by Leonardo on AnB, 11 and 12v (fig. 50), draining or supplying the upper intercostal spaces. Beyond the junction of the azygos, the main stem of the vena cava continues upward to finally divide into two more or less equal branches, corresponding to what are now known as the innominate veins, each of which divides into an internal jugular, accompanying the common carotid artery, and a subclavian vein.
But all this must be assigned to Leonardo’s earlier days when he was more under the influence of Avicenna. Later he certainly recognized the existence of the right atrium, speaking of it as an upper ventricle; when figure 44 was drawn he recognized that the superior and inferior venae cava? were not continuous, but both opened into the right atrium; in figure 45 he shows the pulmonary artery arising from the right ventricle, quite distinct from the vena cava; and later he maintained that both arteries and veins arise from the heart. His own observations revealed to him the errors of his predecessors which he at first accepted.
Many of Leonardo’s observations on the blood-vessels w r ere based on his dissection of il vecchio (see p. 53), and in connection with one of the figures made from this dissection (AnB, 32v) he records a timehonored belief, based on experiments performed by Galen, to the effect that if both carotid arteries and jugular veins are tied, the victim suddenly falls to the ground unconscious as if dead, nor will he ever recover if the ligatures are allowed to remain for even the hundredth part of an hour. It is as a result of this belief that Leonardo speaks of the jugulars as the venae apoplectiche, a term probably borrowed from Mondino, who states that they are also called venae somni, since sleep is caused by the natural blocking of their branches. Avicenna terms the carotids art. sopor arice (subeticce).
Fig. 53. Dissections of heart, lungs, abdominal viscera and blood-vessels. (QIII, 10v.)
Fig. 54. I lie irreat vessels of a centenarian. (AnB, 33.)
Leonardo has left no systematic account of the blood-vessels, he considers them piecemeal, but when one has collected all the pieces one finds that the majority of the principal vessels have been described or figured. The veins, on the whole, are more fully represented than the arteries as was customary, since they were more obvious, being gorged with blood while the arteries were empty. There are, however, many gaps and many imperfections in the story, especially when he is dealing with the arteries of the limbs.
The coronary vessels supplying the walls of the heart are well shown on QII, 4 (see also fig. 44) and, as an indication of Leonardo’s sharpness in observation, it may be mentioned that he speaks of the great cardiac vein ( vena nera ) that winds around the heart in the atrio-ventricular groove as running in the opposite direction to the accompanying artery (ssi fa inchontro all arteria), meaning thereby that as one traces the vein toward the back of the heart it grows larger, becoming the coronary sinus, while the artery grows smaller. He recognizes three distinct veins, two of which are accompanied by arteries and mark the boundaries of the right ventricle; the third, however, the posterior vein of the left ventricle, seems to have no companion artery and he makes a note to ascertain by further observation whether this was really the case (QIV, 13v).
It is strange that he does not describe nor figure the external carotid artery, unless it be intended on QIV, 9v, but he does represent several of its branches without tracing them back to their origin. Thus he shows the superficial temporal and internal maxillary arteries on AnB, 42, while the infraorbital branch of the latter is again shown on AnB, 12, and the intracranial portion of its middle meningeal branch on AnB, 41. Of these meningeal branches he notes that they are half buried in grooves on the inner surface of the skull and are covered over by the membrane of the brain, the dura mater. The lingual artery is shown more fully, but it is made to arise from the internal carotid; there is an excellent figure of its terminal ranine branch on QIII, 10. Of the veins of the head the anterior facial is shown on AnB, 12, and again uniting with the posterior facial to form the external jugular (QV, 17; 20v), while the veins of the forehead and lateral portions of the scalp are shown on AnB, 1 and Iv.
The branches of the subclavian artery can not be identified with certainty, but the vertebrals seem to be indicated on AnB, 32 v. Pectoral branches connected with the axillary vessels are also shown on the same folio, but the arteries of the arm are almost neglected, being shown only toward the wrist where they appear from under the muscles that cover them (AnA, 12v, 13v). On the other hand the superficial veins of the arm arc repeatedly figured (AnA, 4, 0 and 12v; AnB, 10 and 32v; QIY, 9v) (figs. 51, 55) and the network formed by anastomoses of the mammary and pectoral veins is well shown on AnA, G (fig. 55). Leonardo studied the veins of the arm on the living as well as by dissection, for he makes a memorandum to “draw the arm of Francesco, the miniaturist, which shows many veins” (AnB, 10), and possibly the drawing on the same page as the memorandum (fig. 51) represents the arm of Messer Francesco.
Of the branches of the descending aorta the coeliac artery, with the beginnings of its hepatic and splenic branches, and the superior mesenteric are shown on AnB, 13v, the last being described as nourishing the root of the zirbo (omentum), its distribution having been confused with that of the right gastro-epiploic. The renal veins are shown in many figures (fig. 46) and the arteries on AnB, llv and 13v. The internal spermatic vessels are also figured, sometimes one or both arteries, sometimes one or both veins, and both arteries and veins on QIII, 1 Ov (fig. 53) ; it is interesting to note that the left vein is correctly shown, opening into the right renal vein instead of into the vena cava (figs. 46, 53), an arrangement, however, that might have been learned from Avicenna, who adopted it from Galen’s description written several centuries earlier. Below, the aorta and vena cava end by dividing into the common iliacs, and just before the artery divides it gives off a branch that runs directly downward (QIII, 4v, 5 and lOv; QIV, 7) and seems to be the caudal artery, corresponding to the human middle sacral (fig. 53).
In his earlier drawings, Leonardo figures of the portal system of veins only the splenic and this, together with what is probably the splenic artery, is shown passing directly from the liver to the spleen (QI, 12; QIII, 5, lOv; QIV, 7) (figs. 4, 46, 53, 56), Leonardo having, apparently, been deeply influenced by the theory of black bile and its passage to the spleen. On AnB, llv, and again on AnB, 34v, the artery is represented as arising from the aorta and quickly dividing into what are evidently the hepatic and splenic branches, and what may be intended for the left gastric artery is also shown on AnB, 34v (fig. 56). In both these figures, however, the vein still passes directly from one organ to the other, receiving in the AnB, llv figure the left internal spermatic vein (evidently a slip since that vein is correctly shown on QIII, lOv (fig. 53) joining the left renal) and in those on AnB, 22 and 34v (fig. 56) the right gastro-epiploic vein, the artery having a corresponding branch. In the text of AnB, llv the vein is described as arising by five branches from the liver, a branch corresponding to each of its penulx (lobes), an idea adopted from Mondino, and at about the middle of its length it gives off a branch that passes to the base of the omentum (zirbo); farther along a branch passes upward to the left lower portion of the stomach, probably one of the gastric branches of the splenic vein, and finally the vein terminates by dividing into two branches at the spleen. This arrangement of the vein and its branches is also shown on AnB, 3. It may be noted that the figures on AnB, 3, llv, 22 and 34v are based on the dissection of il vecckio. It is strange that the participation of the mesenteric veins in the formation of the vena porta is nowhere clearly figured, notwithstanding that they were essential to the accepted theory as to the function of the liver in concocting into blood the food-substances brought to it by these veins from the upper part of the intestine, as well as by those from the stomach. The latter were the more important and it is possible that having noted the right gastro-epiploic vein from the region of the stomach, Leonardo did not consider it necessary to look farther, a supposition that might account for his conjecture that the branches of the superior mesenteric artery were distributed to the omentum. This supposition is not advanced in extenuation of Leonardo’s carelessness in this part of his dissection, but merely as a possible explanation of that carelessness. He does, however, represent a fragment of the vein on AnB, 3, and mentions it in the text as —
“The ramification of the mesentery, which joins all the intestine, returning to this the blood that dies and taking from it the new nourishment, just as the roots of any herb or plant mingle with the earth that covers them and suck from that the humor that nourishes them.”
Furthermore, he says on the same page —
“In the mesentery are planted roots of all the veins that unite at the porta of the liver and purify the blood in this liver. And it then enters the vena del chilo (vena cava) and this vein goes to the heart and makes the blood more noble, and this enters the artery (as) spirituous blood.”
Fig. 55. Superficial pectoral and epigastric veins. (An A, 6.)
Fig. 56. I’ inures of the liepjitic artery and portal vein. (AnH, 34v.)
He apparently failed to observe the mesenteric arteries for he has a note (AnB, 3) to “see if the mesentery has arteries or not.”
The division of the common iliac vessels into the external and internal iliacs is shown on QIII, 4v and lOv (fig. 53), but the account of the branches of the internal iliacs is very incomplete and probably based, so far as it goes, on animal dissections. In a drawing on AnB, 6v (fig. 57) the left common iliac vein is shown coming from the right side of the vertebral column and it continues as the external iliac over the brim of the pelvis, giving off a branch which passes down into the pelvis. In addition, two other large branches are shown, one ascending, evidently the ilio-lumbar, and one descending, which resembles the lateral sacral; it gives off two branches that make their way through the obturator foramen. A more detailed, but at the same time an incomplete and somewhat confused statement as to the pelvic veins is given on QIII, 7v:
"The first branching of the great vein below the renals is where the spinal column unites with the sacrum ( alchatim ); the second are the branches which divide to nourish the coccyx (? spina della calucda); the third is in the inestri of women and the uterus; the fourth in the bladder; the fourth, a finger and a half further on, goes to the testicles; the fourth arises a finger and a third distant from this and passes out of the abdomen ( sifac ) and divides into two, and one is the saphenous and the other ...”
The various branches indicated are the common iliacs, the lateral sacrals, the uterine, a vesical, the ovarian, and the external iliac, which divides into the saphenous and femoral. On AnB, 36v mention is made of the hiemorrhoidal veins.
"Divide the subject through the middle of the spine; but first tie the chilo (vena cava) and the artery, so that they do not empty, and thus you will be able to see the haemorrhoidal veins on either side, i.e. in each division of the subject.”
One doubts whether the preparation was ever made, although there is a sketch representing it which shows a vein arising from what seems to be an obturator vein and ramifying in the region of the pelvis that would be occupied by the upper part of the rectum.
Quite early in his anatomical studies, Leonardo must have had opportunity for dissecting a fetal mammal, perhaps the calf that is represented, enclosed within the chorion, on AnB, 38 (fig. 84). In it he might have observed the hypogastric arteries passing up the abdominal wall to the umbilicus from the internal iliacs and the umbilical vein passing from the umbilicus to the porta of the liver. So indeed he figures them on AnB, 29v (fig. 87), but, curiously, he assumes that they also occur as functional blood-vessels in the adult human body and he represents them in such drawings as that on QI, 12, and those drawn from il vecchio on AnB, 4, 22 and 34v (figs. 58, G4). The umbilical vein in the adult is represented by a solid cord, the so-called round ligament of the liver, but Leonardo shows it (fig. 58) as a patent vein, branching in the substance of the liver (AnB, 4, 34v), just as does the portal vein. The hypogastric arteries are also represented by solid cords in the adult, but Leonardo shows them as open arteries and furthermore shows them accompanied by veins, the artery and vein of each side uniting to form a single trunk before reaching the umbilicus (AnB, 4, 34v). These veins are, of course, figments of the imagination, presented, perhaps, on the supposition that every artery has a companion vein (sec p. 170).
The representation of the vessels of the lower limb is as incomplete as that of the vessels of the upper. The femoral vessels, in their upper part, are shown on AnB, 8 and on QIV, 8, and their course through the adductor canal is shown on AnB, IS, the sartorius muscle being cut away to expose them. But, as in the upper limb, it is the superficial veins that attract chief attention and the arteries are neglected. The saphenous vein is shown throughout almost its entire course on QV, 3v, and in its upper part on AnB, 8, where it is accompanied by an artery, and on QIV, 8, where the superficial epigastric is shown opening into it. These latter veins are also well shown on AnA, 6 (fig. 55).
Fig. 57. The iliac vein and its branches. (AnB, 6v.)
Fig. 58. Hypogastric vessels and umbilical vein. Above is a frontal section through cervical vertebra 1 showing the costotransverse foramina. (AnB, 4.)
Of the vessels of the lower leg little can be said. The small saphenous vein is shown on AnB, 7, and possibly on AnB, 7v. A somewhat curious representation of the vessels behind and below the knee-joint occurs on AnB, 7. A nerve, the posterior tibial, occupies the mid-line with an artery on one side of it and a vein on the other; each of these vessels gives off a branch, which passes medially behind the nerve, and, the two branches crossing each other, there is below an artery and a companion vein on each side of the nerve. This is probably a representation of the formation of the peroneal vessels from the posterior tibials. There are no figures or descriptions of the plantar vessels, but what seems to be the dorsalis pedis artery is sketchily shown on AnB, 7v.
Leonardo’s first uncertainty regarding the pulmonary vessels has already been noted, but he seems to have made one important discovery in connection with them, namely, that there are passing to the lung special bronchial vessels, quite distinct from what are usually termed the pulmonary vessels. His statement regarding these arteries is as follows :
“You may say that the trachea and the lung have to be nourished, but if you had to do with a single large venarteria, this could not accompany the trachea without great interference with the movement which the trachea makes in its dilation and contraction, as well in length as in thickness; wherefore for this She (Nature) gave a vein and an artery to the trachea, which would be sufficient for its life and nourishment, and the other large branches She separates somewhat from the trachea to nourish with more convenience the substance of the lung.” (QII, 1.)
His figure shows two bronchial arteries arising apparently from the aortic arch and ramifying upon the walls of the bronchus through all its branches. He seems to have recognized the bronchial arteries.
The suggestion that Leonardo may have had an idea of the circulation of the blood has been made more than once, and first of all by Richter (1883), who first made a thorough study of the manuscripts. Richter based his suggestion on Leonardo’s statement that the blood that returns to the ventricle is not that which closes the valves, and also on one of the comparisons of the microcosm with the macrocosm. The latter is not pertinent, nor, indeed, is the former, since it is merely a restatement of the belief that on the contraction of the ventricle the portion of its blood that lay between the cusps of the valves passed back into the atrium, while the remaining portion forced the cusps together and closed the opening. Roth (1907) regards the suggestion as improbable, and while Holl (1910) is at first inclined to accept it, he later (1911) doubts, while expressing a belief that if Leonardo had continued his studies he might have discovered the true state of affairs. Boruttau (1913) takes the same position remarking — is it in irony? — that if Leonardo had practised surgery or vivisection or had had the advantage of the use of the microscope to show him the capillary circulation, he would no doubt have perceived the true state of affairs. If Erasistratus had had a microscope he too might have discovered the circulation! More recently Hopstock (1919), while admitting that the matter is still open to discussion, expressed the opinion that it is not impossible that Leonardo may have seen circulationum sanguinis with his inner eye. He bases this opinion on (1) a passage on AnB, 3 —
“By the ramifications of the vena del chilo (vena cava) in the mesentery the aliment from the corruption of food in the intestine is attracted and finally returns by the extreme ramifications of the artery to the intestine, where, being dead blood, it is corrupted and takes on the fetor of the feces
And (2) a passage on AnA, 4, ci propos of the microcosm idea, which has already been quoted (p. 97).
The passage on AnA, 4, does suggest a circulation of the w r aters of the macrocosm, but it contrasts rather than compares the conditions of the blood in the microscom. Similarly the passage on AnB, 3, does suggest a circulation, but it deals with a special case, it is incorrect in statement, it is obscure in that it does not explain how the blood could pass to the artery and, furthermore, it does not describe a continuous circulation, but a method of disposal of useless, dead blood. Hopstock makes out a stronger case than Richter, but even so the passages quoted are unconvincing in the light of Leonardo’s definitely expressed beliefs as to the movement of the blood in the heart and as to the significance of venous and arterial blood. It was the doctrine of the pneuma that delayed the discovery of the circulation of the blood for centuries after the valves of the heart and their action were known. If the Galenic teaching that the blood of the veins was for nutrition and that of the arteries was for imparting energy were accepted, there was no incentive to seek for any connection between the two sets of vessels — indeed any such connection would be disadvantageous. And so it was left for Harvey in the seventeenth century to overthrow the time-honored doctrine by an accumulation and logical presentation of pertinent facts, which allowed no other conclusion than that there was a circulation and therefor a connection between the arteries and veins, a connection that was actually demonstrated later by Malpighi.
One of Llarvey’s strong arguments in favor of the circulation was based on the amount of blood pumped by the heart. It has been seen (p. 165) that Leonardo also attempted to estimate this amount, but did not carry his results far enough. They left him, however, with the problem of what became of all the blood that passed through the heart. The passage from AnB, 3, quoted above (p. 178), is an attempt at a solution and on AnB, 34v there is a second similar attempt.
“Of the two larger veins that come from the liver to the spleen and come from the larger veins of the spine (aorta ?), I judge that they are collectors of the superfluous blood, every day removing it by the meseraic veins and depositing it in the intestines, with the same fetor when it has arrived in these as the whole would have in the dead from the tomb, and this fetor is that of the feces.”
Apparently the meseraic veins from the upper part of the intestine were supposed to carry food material to the liver to be manufactured into blood, but those of the lower part of the intestine carried superfluous, dead blood to the intestine.
Vital spirits are also being continuously produced and there must be some way for disposing of the excess. Leonardo meets this difficulty by supposing that —
“Mingled with heat and inspissated moisture ( umito spesso ) it evaporates through the tips of the small veins ( vena chapillari ) at the surface of the skin in the form of sweat.” (QII, 11.)
He refers to a case he claims to have seen, that of a man whose heart burst while he was fleeing from his enemies and he emitted sweat mingled with blood from all the pores of the skin (QIV, 13). It seems strange that with his knowledge of the heart-beat Leonardo did not see in it the vis a tergo that forces the blood to the uppermost parts of the body. On CA, 171 he states that —
“The cause that moves the humors in all kinds of animated bodies against their natural weight is the same as that which moves the water enclosed within them through the terrestrial veins and distributes ( distingue ) it through subtle pores, and as the blood from below surges upward and is shed through the ruptured veins of the forehead and as the water rises from the lower parts of the vine to its divided branches, so too from the lowest depths of the sea the water ascends to the summits of the mountains, and there finding the natural veins it falls through these and returns to the sea below. Thus within and without it goes changing, sometimes rising upward with accidental motion, sometimes descending with natural freedom. So joined together in a continuous revolution it goes circulating ( girando ).”
This might be taken as another piece of evidence that Leonardo had some sort of perception of the circulation of the blood, but there is no suggestion of a passage of the blood from veins to arteries or vice versa, merely a flow from and to the heart. It is how the blood reaches the head, how the sap ascends in the plant and how water comes to be found far above the sea-level, it is these problems that disturb him. Bottazzi (1910) referring to the passage just quoted suggests that the inexorable analogy of the two living beings, the greater and the lesser, so conquered the spirit of Leonardo as sometimes to diminish his penetrative powers. It seems to have done so in this case, for he returns to his problem elsewhere and maintains that the water ascends from the sea to the mountain tops by the same cause that carries the blood to the head (A, 55v), and in still another passage he defines the cause, stating that blows on the head should not cause bleeding since the veins should be able to contain all the blood that is there and blood should not ascend; the cause of the bleeding is that the heat mingled with the blood desires to return to its element and draws the blood with it (A, 56v).
An early sketch of the digestive tract and longitudinal and transverse sections of the penis. (QIII, 3v.)
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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. (2021, May 7) Embryology Leonardo da Vinci - the anatomist (1930) 13. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Leonardo_da_Vinci_-_the_anatomist_(1930)_13
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