CHAPTER IY. 



CIRCULATION OF THE BLOOD. 



Discovery of the circulation Physiological anatomy of the heart Valves of tne 

 heart Movements of the heart Impulse of the heart Succession of move- 

 ments of the heart Force of the heart Action of the valves Sounds of the 

 heart Cause of the sounds of the heart. 



HARVEY discovered the circulation of the blood in 1616, 

 taught it in his public lectures in 1619, and in 1628 published 

 the " Exercitatio Anatomica, de Motu Cordis et Sanguinis 

 in Animalibus" It is justly said by Flourens, in his ele- 

 gant little work on the discovery of the circulation, that 

 from this discovery dates the epoch of modern physiology, 

 when tradition began to give place to observation. When 

 we reflect that it is through the medium of the blood that 

 all the processes of life take place ; that all tissues are nour- 

 ished by it, and all fluids formed from it ; that it gives fresh 

 material to every part, and takes away that which is worn 

 out ; that it carries oxygen to every part of the system, and 

 gives to each structure its vital properties ; we can form some 

 idea of the state of physiology before anything was known 

 of the circulation. This momentous discovery, from the 

 isolated facts bearing upon it which were observed by nu- 

 merous anatomists, to its grand culmination with Harvey, so 

 fully illustrates the gradual development of most great phy- 

 siological truths, that it does not seem out of place to begin 

 our study of the circulation with a rapid sketch of its history. 



