Vesalius's attack on Geminus: some new evidence

In the China root letter of 1546 Vesalius castigated the author of the Compendiosa (Geminus) for reducing the size of his illustrations and for misrepresenting the courses of the vessels and nerves. It is interesting to enquire whether these complaints were justified.

It is true that Geminus's illustrations are smaller than the largest of Vesalius's, which are printed on fold-out sheets, but the difference in sizes of the not very great.

To examine the more demanding question of whether the courses of the vessels and nerves are different in Geminus than in Vesalius, one of us (IMLD) devised a method of making a direct visual comparison between the plates. This relies on the ability of modern image-processing software to superpose images while keeping the identity of each distinguishably separate. Briefly, the images from Vesalius and Geminus are scaled to be of the same height and, if necessary (some of Geminus's images are left-right inversions of those of Vesalius) the Geminus image is 'flipped' left to right. The line images are then given false colours, greenish-blue for Vesalius and brick-red for Geminus and superposed as nearly as possible. The result is that areas which occur only in Geminus appear blue-green, those present only in Vesalius are gold, and where the images overlap the result is red or blue. Thus, the complex and similar paths of the lines in the two images can be distinguished and their relationships examined1. The two versions of Vesalius's large fold-out illustration of the course of the nerves were compared.

[Fig .. course of nerves: nervorum delineatio, Vesalius alone, Geminus alone, 
						superposition; magnification of an area in thigh]

It is apparent that, although there are many areas where the images do not exactly superimpose, the paths of the nerves are very closely similar indeed and that for virtually every branch in the one image there is one closely corresponding in the other. The failure of exact superposition is caused by multiple, small, local differences in orientation and scale. Since, in any case, the diagrams represent typical paths for the branches and there are small differences between their courses in individual subjects these differences between Vesalius and Geminus do not represent consistent or significant differences in the anatomy. Far from Geminus having misrepresented Vesalius he has reproduced the courses of the nerves as shown by Vesalius remarkably faithfully. If one compares the cerebral and hepatic blood vessels in the same way the conclusion is the same.

[Link to superposition of hepatic portal venous circulation. Click for larger image (1Mb)]
[Left click for larger image (2Mb)]

It seems very probable that Vesalius had not seen Geminus's work and was criticising it on the basis of second-hand reports and perhaps of information about the overall size of the largest sheets in his and in Geminus's books. The claim that the course of the nerves and vessels shown in the original woodcuts has been misrepresented in the engraved copies is unfounded.

1. Donaldson, IML Two States of Some Plates in the Compendiosa of Thomas Geminus (1545) The Library 2010 11: 89-104.

© 2005 Edinburgh University Library / Royal College of Physicians of Edinburgh
05 April 2006