CHAPTER XXV 

 CIRCULATION 



" The circling streams, once thought but pools of blood, 

 (Whether life's fuel or the body's food) 

 From dark oblivion Harvey's name shall save." 



Dryden. 



The inland transport system that we have had under consideration 

 differs materially from our canal system. Not only are the barges 

 submersed in the plasma, but the force which carries them along 

 is the force which causes the plasma itself to move. The water- 



FiG. 85. — Vertical Mesial Section through Heart to show Aortic and Mitral Valves. 

 R.V., right ventricle; L.V., left ventricle with papillary iimscle ; L.A., left atrium with 

 the mitral valve extending into the left ventricle ; Ao., aorta with anterior cusp on top of 

 .septum. 



(Noel Paton's Essentials of Human Physiology.) 



ways are a series of elastic-walled tubes forming a closed circuit. 

 In this circuit is a central pumping station, the heart, which keeps 

 the blood in motion. The accompanying figure (Fig. 85) is a 

 diagrammatical view of a vertical-mesial section through the 



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