158 



PHYSIOLOGY 



CHAP. 



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

 running centrifugally and another running cen tripe tally, which 

 are closed, and communicate 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 o. 

 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- 

 stole. 



The discovery of the Circula- 



uiir; ir:iu ii'Miii, HI wiittni UI I ' t M ( 'I l.U U1UUU , / .- T"*l 1 J * 1 J 1 



circulates. Blue indicates the vessels tlOn Ol the BlOOd IS Certainly the 

 connected witli the right heart, in which 

 circulates the venous blood. Yellow in- 

 dicates the lymphatic system, pc, Lesser, 

 or pulmonary circulation ; p, lung ; gc, 

 great or systemic circulation, formed by 



Fie. 4/>. Diagram of cardio- vascular system 

 lied indicates the vessels connected witl 

 the left heart, in which the arterial blood 



im-iv^f anf oirnnf va^rvrrl^rl in 



important event recorded in 



the history of physiology. By it 

 , , J .. ,* J & J , J . 



nearly the whole System of phySlO- 



all the vessels of the aortic arterial system, -i i i JTll 1J 



and the venous system of the venae cava ; logical and inedlCal knowledge, aS 



SpCSc i rS m 1\tO y v S S,. ce ' 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 



