The description of the heart follows Mondino closely. Occasionally a phrase or two is reminiscent of Mondeville. The trite conception of the heart as a king in its necessarily central position was very frequently repeated by writers in the Middle Ages. To Harvey, who had a certain mediaeval element in his mentality, it seems to have appealed, and he used it in his _Prelectiones Anatomiae_,[202] and chose it to introduce his great work on the circulation of the blood.[203] The heart was similarly described as ‘flame-shaped’, because it was regarded as the source of animal heat. The idea that it is the first to live and the last to die comes from Aristotle.[204] The _bone_ in the heart also comes from Aristotle.[205] The idea was quite familiar to mediaeval anatomists, who frequently endeavoured to identify the _bone_ with the firm tissue around the orifices of the aorta and pulmonary artery. The reader may be reminded that a true ‘os cordis’ is in fact to be found in some mammalia. Mondino, followed by Manfredi, describes the action of the heart and blood-vessels mainly according to the views of Galen, but without any very clear or connected statement. The ‘third ventricle’ especially has its origin in a misunderstanding. This mythical structure is an attempt to combine the views of Aristotle and of Galen. Aristotle, who probably never dissected a human body, derived his anatomical conceptions largely from cold-blooded animals, in some of which the heart is provided with three cavities. He considered that the heart had three chambers, the largest being on the right, the smallest on the left, and one of intermediate size between the two. As far as they can be identified, the largest was the right ventricle plus the right auricle, the smallest or left chamber was the left auricle, while the intermediate cavity appears to have been the left ventricle.[206] Galen’s description differed altogether from that of Aristotle. He tells us expressly and somewhat contemptuously that ‘it is no marvel if Aristotle erred in many anatomical matters, a man who thought forsooth that the heart in the larger animals had three chambers’.[207] Galen always describes the heart as having but two chambers, the right and left ventricles, a wholly subordinate part being assigned to the auricles. These latter were regarded as safety-valves, expanding to hold superfluous blood when the chambers of the heart to which they correspond become overfilled. [Illustration: Fig. 21. THE HEART From the Roncioni MS. (Pisa 99) after Sudhoff.]