Introduction: Aristotle’s writings on medical topics remained unchallenged for almost 2000 years. It was Vesalius, in his monumental work De humani corporis fabrica, published in the 16th century, who wrote that sometimes the left kidney was higher than the right, contradicting Aristotle and Galen. In this paper, we trace another mistake, again by Aristotle, on the location of the kidneys. Material and Method: We carefully read the Aristotle’s writings concerning the location of each kidney of a cow in each site of the back bone and his extrapolation that this is also true for the humans. We then studied references from current zoological articles about the location of the kidneys in a living cow. Based on clinical examinations and laboratory findings, it was shown that both kidneys are located in the right side of the animal, because the rumen part of its stomach pushes the left kidney to the right of the backbone. When the animal is slaughtered or after fasting, the rumen deflates; thus the left kidney returns back to its normal side. Conclusion: As Aristotle studied dead animals, he was right in his observation but absolutely wrong when interpreting it as applying to a living cow, a human and to all other species.
Key words: Aristotle and the location of the kidneys, Vesalius and the kidneys, Autopsies in Byzantium, Vivisection