SECTION VII 



THE CIRCULATION 



I. General Arrangement 



THE arrangement by which the blood and lymph are dis- 

 tributed to the tissues may be compared to a great irrigation 

 system. 



It consists of a central force pump the systemic heart 

 (Fig. 105, S.H.) from which pass a series of conducting tubes 



LUNG 



CAP 



FIG. 105. Scheme of the Circulation. S.H., Systemic Heart sending Blood to the 

 Capillaries in the Tissues, Cap. The Blood brought back by Veins and 

 the exuded Lymph by Lymphatics, Ly. t passing through glands ; Blood sent 

 to the Alimentary Canal, Al.C., and from that to the Liver, Liv. ; Blood also 

 sent to the Kidneys, Kid. ; the Blood before again being sent to the body is 

 passed through the Lungs by the Pulmonic Heart, P.H. 



the arteries leading off to every part of the body, and 

 ending in innumerable fine irrigation channels the capil- 

 laries (Cap) in the substance of the tissues. From these, a 

 considerable proportion of the blood constituents is passed 

 into the spaces between the cells as lymph. From these 

 spaces the fluid is either passed back into the capillaries, or 

 is conducted away in a series of lymph vessels, which carry 

 it through lymph glands (Ly.\ from which it gains certain 



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