158 



PHYSIOLOGY 



CHAP. 



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

 running centrifugally and another running centripetally, which 

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



of the lesser, or pulmonary, circula- 

 tion unites the ventricle of the 



v n///7 ^j^^aF^s^ * right with the auricle of the left 



$ wi?m30^ ^ heart ; the system of the great, or 

 rWo //jiBS^' ri TJ?T*iS^ aortic, circulation connects the 

 ^ (I M W.^$& 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 orifj 

 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 'Ol' 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 

 circulate the blood, emptying 

 its contents into the arteries during 

 systole, tilling itself again with 

 blood from the veins during dia- 



FIG. 45. Diagram of cardio-vascular system. klOltJ. 



Red indicates the vessels connected with The disCOVCrV of the CirCllla- 

 the left heart, in which the arterial blood ,. ~ .-. T>I j L- i .Li- 

 circulates. Blue indicates the vessels tion oi trie rJloocl is certainly trie 



connected with the right heart, in which mna i^^^f.nnf-. a^nf. iv^nrded ill 



imvnrtar>f a\rmif 

 circulates the venous blood. Yellow in- ' important event 



dicates the lymphatic system, pc, Lesser, the MstOl'V of physiology. By it 

 or pulmonary circulation ; p, lung ; gc, i i V ^ i 



great or systemic circulation formed by nearly the WllOle System OI phySlO- 



logical and medical knowledge, as 

 i." 1 Banded 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 



