158 



PHYSIOLOGY 



CHAP. 



cc 



and a left or arterial heart, connected by a system of vessels 

 running centrifugally and another running centripetally, which 

 are closed, and comnmnicate by a capillary system. The system 



of the lesser, or pulmonary, circula- 

 tion unites the ventricle of the 

 right with the auricle of the left 

 heart ; the system of the great, or 

 aortic, circulation connects the 

 ventricle of the left heart with the 

 auricle of the right. The auri- 

 culo- ventricular orifices and the 

 orifices of the two big arteries 

 which arise from the ventricles are 

 provided with valves ; the orifices 

 of the great veins, which open 

 into the auricles, have no valves, 

 although on the other hand valves 

 are plentiful along the course of 

 the veins. 



The importance of the several 

 parts of the circulatory system is 

 very different. Only the capillary 

 portion serves the physiological 

 uses of the blood. The arteries 

 and veins are only paths to con- 

 duct the blood to the seat of its 

 activity, whence it is again returned 

 to the heart. The heart is the 

 motor, a perfect pumping machine 

 to circulate the blood, emptying 

 its contents into the arteries during 

 systole, filling itself again with 

 blood from the veins during dia- 



' 



The discovery of the CirCllla- 

 - 



Kic. 4. r i. Diagramof cardiovascular system. 

 Ke<l indicates the vessels connected with 



the left heart, in. which the arterial blood . e , , -ni j i j_i 



circulates. Blue indicates the vessels tlOn OI the .BlOOd IS Certainly tile 



connected with the right heart, in which ^-.^f irrmnrrant pvpnt rppnrrlprl in 



circulates the venous blood. Yellow in- "lOSE important event ] 



dicates the lymphatic system. p; Lesser, the history of physiology. By it 

 or pulmonary circulation; p, lung; gc, 111 r i 



.nn-at or systemic circulation, formed by nearly the Whole System OI ph} r S10- 



all the vessels of the aortic arterial system, i in j- i i i.j 



lOglCalaild UieellCal IvUOW ledge, a 



and the venous system of the venae cava ; 



S^dffl^"?5C?Si^ handed down from Antiquity re- 



ceived a violent wrench, and under- 

 went a fundamental reconstruction. With it begins the modern 

 science of physiology, founded on the ruins of the ancient doctrine. 

 It is indispensable that any one who aspires to physiological 

 culture should be acquainted at least in its main points with the 

 history of this great discovery (which has been misrepresented in 



