THE CIRCULATION OF THE BLOOD. 447 



is it, observes Cuvier, that we are often on the brink of a discovery 

 without suspecting that we are so ; so true is it, we may add, that a 

 certain succession of time and of persons is generally necessary to 

 familiarize men with one thought, before they can advance to that 

 which is the next in order. 



Sect. 2. The Discovery of the Circulation made by Harvey. 



WILLIAM HARVEY was born in 1578, at Folkestone in Kent. 14 He 

 first studied at Cambridge : he afterwards went to Padua, where the 



o ' 



celebrity of Fabricius of Acquapendente attracted from all parts those 

 who wished to be instructed in anatomy and physiology. In this 

 city, excited by the discovery of the valves of the veins, which his 

 master had recently made, and reflecting on the direction of the valves 

 which are at the entrance of the veins into the heart, and at the exit 

 of the arteries from it, he conceived the idea of making experiments, 

 in order to determine what is the course of the blood in its vessels. 

 He found that when he tied up veins in various animals, they swelled 

 below the ligature, or in the part furthest from the heart ; while arte- 

 ries, with a like ligature, swelled on the side next the heart. Combin- 

 ing these facts with the direction of the valves, he came to the conclu- 

 sion that the blood is impelled, by the left side of the heart, in the 

 arteries to the extremities, and thence returns by the veins into the 

 right side of the heart. He showed, too, how this was confirmed by 

 the phenomena of the pulse, and by the results of opening the vessels. 

 He proved, also, that the circulation of the lungs is a continuation of 

 the larger circulation ; and thus the whole doctrine of the double cir- 

 culation was established. 



Harvey's experiments had been made in 1616 and 1618; it is 

 commonly said that he first promulgated his opinion in 1619 ; but 

 the manuscript of the lectures, delivered by him as lecturer to the 

 College of Physicians, is extant in the British Museum, and, contain- 

 ing the propositions on which the doctrine is founded, refers them to 

 April, 1616. It was not till 1628* that he published, at Frankfort, his 

 Exercitatio Anatomica de Motu Cordis et Sanguinis ; but he there 

 observes that he had for above nine years confirmed and illustrated his 

 opinion in his lectures, by arguments grounded upon ocular demonstra 

 tions. 



" Cuv. p. 51. 



