warmer any part is the greater its supply of blood; or otherwise, where the blood is in the largest quantity, there also is the heat the highest."
The Prelectiones are but notes to assist Harvey whilst lecturing, and it is therefore impossible to know what interpretation to place on them, but I think it highly probable that in the course of years Harvey, as his physiolo- gical knowledge increased, modified his views of the connection between animal heat and the heart, for in the Prelectiones he speaks of the heart as the fons totius caloris, and calls it are et domicilium caloris, from which it appears that in 1616 he still held the Aristotelian opinion of the heart being the source of heat.
No portion of the Prelectiones show more strikingly the closeness of Harvey's observa- tion, the amount of his knowledge, and the acumen of his reasoning than that relating to the exposition of the anatomy and the func- tions of the lungs. In his description of them and the pleuræ he makes constant references to their morbid anatomy and their embryonic condition. IIe is evidently in doubt whether the lungs expand and contract from their
