Anatomical Variability


Anatomical Variability vs. the Classical Ideal of a Canonical Human Anatomy

This has been a subject of some interest in Vesalian studies (Straus & Temkin 1943, Siraisi 1994, Hast & Garrison 2000). Polyclitus' 5th century BC canon of human proportion, illustrated by his his statue of the Doryphoros or spear-carrier and explained in his treatise titled The Canon, was a significant antecedent to Plato's doctrine of ideal cosmic forms. But by the time of Galen it was clear to anatomists that any practical guide to dissection must take account of variability. When Renaissance teachers like Vesalius abandoned the teaching of anatomy by the book and relied on actual human specimens as their chief authority, they remembered what Galen said about variability in dissection manuals such as On Anatomical Procedures and On the the Dissection of Veins and Arteries. Though they could not agree on the importance of anomalies or whether they should be ignored in the classroom and dissection theater, leading anatomists were well aware of the conundrum they faced. Vesalius was as a rule open to anatomical diversity and shared with other life scientists of his time "a conception of nature that no longer exhibited the feature of uniformity." (P. Rossi in Siraisi 1994, 62).

Of the six anatomical features carrying Vesalius' name (the foramen of Vesalius in the skull, carrying the vein of Vesalius, the bone of Vesalius, a separated tuberosity in the fifth metatarsal bone, the bronchial lymph glands called glandulae Vesalianae, the ligamentum inguinale Vesalianum, and the os Vesalianum carpi, only two are considered statistically "normal" in modern anatomy. But the young Vesalius was unsure what advice to give.

I would think that such arrangements of veins as occur only quite rarely should be considered by the thoughtful anatomist in just the same way as when sometimes a sixth finger in the hand or some other monstrosity comes to out attention. Thus, whenever I see them in public dissections I pass them over in silence as if they were not there, lest undergraduates believe they are observed in all bodies. I have decided that this must be my standard of procedure not only in dissections but also in lecturing on the perfect human body, especially as I have often learned by experience that students are unfailingly interested in those monstrosities. They would, however, have more cause for regret if they got such a body for a full dissection, because it varies considerably from the human standard —unless they had also been many times present at dissections of perfect, not monstrous, humans, and were constantly heedful of Galen's advice given us at the end of the first book of De anatomicis administrationibus. [Book 3, Ch. 7]

Vesalius refers here to a passage where Galen wrote "If ever, when you are dissecting a limb, you see something that contradicts what I have written, recognize that this happens infrequently. Do not prejudge my work until you yourself have seen, as I have, the phenomenon in many examples." (tr. Singer 1956, 30). Vesalius deleted the advice given in the 1555 edition, perhaps because of the growing acceptance of (and positive interest in) variability.

Earlier in the Fabrica, Vesalius gives a compelling display of his interest in variability when describing variations on the human skull. Though the skulls he illustrates (shown here) fall within the range that is today considered normal variability, Vesalius admits only the first (upper left) as "natural," describing the other four as non naturalis. So eager was he to show variability that he went on to show variations in the sutures of the skull that are decidedly not in the range of variability and do not occur in nature, as both Gabriele Fallopio and Bartolomeo Eustachio would protest before the end of the 16th century.

Vesalius' interest in variability, and even what he described as "monstrous," developed further between the first edition of the Fabrica in 1543 and the second in 1555. He added to his craniology chapter a clinical report about cranial deformity he had seen in a two-year-old girl with hydrocephalus and a second, less relevant, report of a man with an enlarged heart. He also promised to describe "countless such cases at greater length in another book" —one of the projected books that he never wrote.

Vesalius' special interest in anatomical variability could have a biographical dimension if we pay attention to the unusual proportions of Vesalius as represented in the frontispiece of both editions of the Fabrica (shown on the home page). This portrait was re-used in both German and Latin editions of the Epitome, as well as the 1546 Letter on the China Root. This is the only known authentic portrait of Vesalius. Though it had long been customary to normalize and even improve upon any human subject in making a portrait, this Vesalius is far from normal. Placed standing next a table that comes up to his waist, his arms are in unmistakable contrast to that of the cadaver he is dissecting, and his general proportions are unusual, as several observers of the portrait have remarked. Would Vesalius have placed himself next to a giant, or are these faults of draughtsmanship, as some have argued? Would the great anatomist have tolerated an anatomically inaccurate, dwarfish portrait of himself in the fronticepiece of his magnum opus, and then compounded the blunder by re-using the offending portrait again and again?

Students of Vesalius will have to draw their own conclusions. No corroborating evidence has come to light about the physical stature and proportions of Vesalius. The question will continue to intrigue anyone considering Vesalius' interest in variability and the ambiguity with which he described this topic.