lungs, which is called the pulmonary circulation, is the one step in real advance that was made between the time of Galen and the time of Harvey. And I would beg you to note that the word "circulation" is improperly employed when it is applied to the course of the blood through the lungs. The blood from the right side of the heart, in getting to the left side of the heart, only performs a half-circle—it does not perform a whole circle—it does not return to the place from whence it started; and hence the discovery of the so-called "pulmonary circulation" has nothing whatever to do with that greater discovery which I shall point out to you by-and-by was made by Harvey, and which is alone really entitled to the name of the circulation of the blood. If anybody wants to understand what Harvey's great desert really was, I would suggest to him that he devote himself to a course of reading, which I cannot promise shall be very entertaining, but which, in this respect at any rate, will be highly instructive—namely, the works of the anatomists of the latter part of the 16th century and the beginning of the 17th century. If anybody will take the trouble to do that which I have thought it my business to do, he will find that the doctrines respecting the action of the heart and the motion of the blood which were taught in every university in Europe, whether in Padua or in Paris, were essentially those put forward by Galen, 'plus' the discovery of the pulmonary course of the blood which had been made by Realdus Columbus. In every chair of anatomy and physiology (which studies were not then separated) in Europe, it was taught that the blood brought to the liver by the portal vein, and carried out of the liver to the 'vena cava' by the hepatic vein, is distributed from the right side of the heart, through the other veins, to all parts of the body; that the blood of the arteries takes a like course from the heart towards the periphery; and that it is there, by means of the 'anastomoses', more or less mixed up with the venous blood. It so happens, by a curious chance, that up to the year 1625 there was at Padua, which was Harvey's own university, a very distinguished professor, Spigelius, whose work is extant, and who teaches exactly what I am now telling you. It is perfectly true that, some time before, Harvey's master, Fabricius, had not only re-discovered, but had drawn much attention to certain pouch-like structures, which are called the valves of the veins, found in the muscular parts of the body, all of which are directed towards the heart, and consequently impede the flow of the blood in the opposite direction. And you will find it stated by people who have not thought much