Achillini, Alessandro (29 Oct 1463 - 2 Aug 1512)
Achillini was an Italian physician who taught in Bologna and Padua, a philosopher sometimes called the second Aristotle who expounded the doctrines of Averroës and wrote largely upon anatomy.
Galen, he pointed out, faced the problems of Renaissance anatomists who presumed the similarity between human and animal anatomy was exact. "In the larger hand there are thirty bones," stated Achillini. "There would be thirty-one if the ninth of Galen was included, but that, however, is a monkey bone."
By the time Andreas Vesalius published On the Fabric of the Human Body (1543), others could cite numerous errors of Galen in the number and shape of the bones, though Vesalius, too, continued to identify many animal parts as belonging to humans. Leonardo played with the confusion between human and animal anatomy by drawing a fanciful foot of a beast based on a human one, a reversal of the common trend.