DISCOVERY OF THE CERCULATIOX. 171 



The facts bearing upon the circulation which were devel- 

 oped before the time of Harvey were chiefly of an anatomical 

 character. Hippocrates and his contemporaries distinguished 

 two kinds of vessels, arteries and veins ; but they regarded 

 the former as air-bearing tubes, as their name implies, in 

 communication with the trachea. Galen, by a few simple 

 experiments upon living animals, demonstrated the error of 

 this view. He showed that blood issued from divided arte- 

 ries, and demonstrated its presence in a portion of one of 

 these vessels included between two ligatures in a living ani- 

 mal. His ideas, however, of the mode of communication 

 between the arteries and veins were entirely erroneous, be- 

 lieving, as he did, in the existence of numerous small orifices 

 between the ventricles. 



In 1553, Michael Servetus, who is generally regarded as 

 the discoverer of the passage of the blood through the lungs, 

 or the pulmonary circulation, described in a work on theology 

 the course of the blood through the lungs, from the right to 

 the left side of the heart. This description, complete as it 

 is, was merely incidental to the development of a theory with 

 regard to the formation of the soul, and the development of 

 what were called animal and vital spirits (spiritus). The 

 same year, by order of Calvin, Servetus was burned alive at 

 Geneva, and nearly every copy of his work was committed to 

 the flames. But one or two copies of this work are now in 

 existence. One is in the library of the Institute of France, 

 and bears evidence, in some pages which are partially burned, 

 of the fate which it so narrowly escaped. 1 



A few years later, Columbo, professor of anatomy at 

 Padua, and Cesalpinus, of Pisa, also described the passage of 

 the blood through the lungs, though probably without any 

 knowledge of what had been written by Servetus. To Cesal- 

 pinus is attributed the first use of the expression, circulation 



1 The physiological portion of the Christtanismi Reslitutio of SERVETUS has 

 been extracted from the original by FLOUREXS, and is published in his little work 

 entitled Histoire de la Decouverte de la Circulation du Sang, Paris, 1854. 



