32 CIRCULATION OF THE BLOOD. 



of the Institute of France, and bears evidence, in some pages that are partially burned, 

 of the fate which it so narrowly escaped. 



A few years later, Columbo, professor of anatomy at Padua, and Cesalpinus, of Pisa, 

 described the passage of the blood through the lungs, though probably without any 

 knowledge of what had been written by Servetus. To Cesalpinus is attributed the first 

 use of the expression circulation of the blood. He also remarked that, after ligature or 

 compression of veins, the swelling is always below the point of obstruction. 



The history of the discovery of the valves in the veins is quite obscure, although pri- 

 ority of observation is almost universally conceded to Fabricius. As regards this point, 

 we can depend only upon the dates of published memoirs, notwithstanding the assertion 

 of Fabricius, that he had seen the valves in 1574. In 1545, Etienne described, in branches 

 of the portal vein, " valves, which he called apophyses, and which he compared to the 

 valves of the heart." In 1551, Amatus Lusitanus published a letter from Cannanus, in 

 which it is stated that he had found valves in certain of the veins. In 1563, Eustachius 

 published an account of the valves of the coronary vein. In 1586, a clear account, by 

 Piccolhominus, of the valves of the veins was published. Fabricius gave the most accu- 

 rate descriptions and delineations of the valves, and his first publication is said to have 

 appeared in 1603. He demonstrated them to Harvey, at Padua ; and it is probable that 

 this was the origin of the first speculations by Harvey on the mechanism of the circula- 

 tion. Shortly after the return of Harvey from Padua in 1602, he advanced beyond the 

 study of inanimate parts by dissections, and investigated animated nature by means of 

 vivisections. As is evident, when we consider the state of science at that time, anato- 

 mists had long been preparing the way for the discovery of the circulation, although 

 they knew little of the functions of the parts they described. The conformation of the 

 heart and vessels, and even the arrangement of the valves of the veins, did not lead them 

 to suspect the course of the blood; but a few well-conceived experiments on living ani- 

 mals have made it appear so simple, that we now wonder it remained unknown so long. 

 Farthermore, these experiments made it evident that there was a communication at the 

 periphery between the arteries and the veins. 



In the work of Harvey are described, first the movements of the heart, which he 

 exposed and studied in living animals. He described minutely all the phenomena which 

 accompany its action ; its diastole, when it is filled with blood, and its systole, when the 

 fibres of which the ventricles are composed contract simultaneously, and "by an admi- 

 rable adjustment all the internal surfaces are drawn together, as if with cords, and so is 

 the charge of blood expelled with force." From the description of the action of the 

 ventricles, he passes to the auricles, and shows how these, by their contraction, fill the 

 ventricles with blood. By experiments upon serpents and fishes, he proved that the 

 blood fills the heart from the veins, and is sent out into the arteries. Exposing the heart 

 and great vessels in these animals, he applied a ligature to the veins, which had the 

 effect of cutting off the supply from the heart so that it became pale and flaccid ; and 

 by removing the ligature the blood could be seen flowing into the organ. When, on the 

 contrary, a ligature was applied to the artery, the heart became unusually distended, 

 which continued so long as the obstruction remained. "When the ligature was removed, 

 the heart soon returned to its normal condition. 



The descriptions given by Harvey were the result of numerous experiments upon liv- 

 ing animals ; exposing the heart of cold-blooded animals, in which the movements are 

 comparatively slow ; studying, also, the action of this organ in warm-blooded animals, 

 after its movements had become enfeebled. As we shall see when we come to describe 

 the movements of the heart, nothing can exceed the simplicity and accuracy of the de- 

 scriptions of Harvey, which are universally acknowledged to be correct in almost every 

 particular. 



Harvey completed his description of the circulation, by experiments showing the 

 course of the blood in the arteries and veins and the uses of the valves of the veins. 



