GALEN AND ARISTOTLE
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ment on the living heart, that they conveyed blood from the lungs. It seems curious that Galen, who was so fond of experiment, never tried a like experiment on the pul- monary veins. Galen’s knowledge of comparative anatomy enabled him to confute Aristotle’s statement that large animals have three cavities in the heart whilst small animals have only two, of which several explanations have been suggested. The horse, he says, has no more than the sparrow, nor the ox than the mouse x . He found the right
1 De Usu Partium , lib. vi. cap. 19; Kuhn, iii. p. 442.
This strange error of Aristotle as to the number of cavities in the heart has given rise to much dis- cussion, and several explanations have been proposed. The ancient anatomists, and indeed modern ana- tomists, at least as late (I think) as the end of the seventeenth century, never thought of the auricles as cavities of the heart , but only as the terminations of the vena cava and pulmonary veins respectively (the term ‘ auricle ’ being confined to the auricular appendix), and separated from the heart proper by the mitral and tricuspid valves on the two sides. Harvey also speaks of the auricles as distinct from the heart (see Willis’s translation, De Motu Cordis, p. 29, note). Hence for them the only possible interpretation of Aristotle’s statement was that he in- tended to say that the heart of large animals had three ventricles. Vesa- lius explains the error thus : that, the upper part of the left ventricle being concealed by and rising up behind the right (anterior) flap of the mitral valve during dissection, this led Aristotle to think that this portion was a third ventricle of the heart ; an error much more excusable, he says, than that of be- lieving the number of ventricles to vary according to the bulk of the animal {De huntant corporis fabrica,
1543, p. 590). Colombo takes the same view. Cesalpino, in defending Aristotle, boldly asserts that there are three ventricles in the heart not only of larger animals, but even of birds, as may easily be seen by making transverse horizontal sections of the heart, beginning with the base. We then see the middle or third ventricle separated from the left by a septum which reaches nearly to the apex. He admits that this is denied by the medical anatomists {Quae- stiones Peripateticae, ed. 1593, lib. v. p. 1 18). Evidently he mistook the right flap of the mitral valve for a septum.
Harvey discusses the question in two places. In the MS. Pre- leciiones (fol. 74) he says he is as- tonished that Aristotle describes three ventricles so precisely : * Nec posset salvari autor tam diligens et fidelis nisi auriculam sinistram pro ventriculo . . though Galen rightly blames him for making a difference between large and small animals. Hence he supposes that Aristotle took the left auricle for a ventricle. But in the De Motu Cordis (cap. xvii) he suggests that the position of the mitral valve perhaps misled Aristotle into thinking the left ventricle to be double {‘quae res imposuit forsan Ari- stoteli ut hunc veniriculum duplicetn sectione per transversum facta exisit- maret ’). Probably he was acquainted with the fallacy of Cesalpino, and
