202 



THE HUMAN BODY. 



and these convey it again to the heart. At certain points 

 in the course of the blood-paths valves are placed, which 

 prevent a back-flow. This alternating reception of blood 

 a.t one end by the heart and its ejection from the other go 



nadu 



del 



FIG. 77. The arteries of the hand, showing the communications or anasto. 

 moses of different arteries and the fine terminal twigs given off from the largei 

 trunks; these twigs end in the capillaries which would only be visible if mag> 

 nified. R, the radial artery on which the pulse is usually felt at the wrist ; 7, 

 the ulnar artery. 



on during life steadily about seventy times in a minute, 

 and so keep the liquid constantly in motion. 



The vascular system is completely closed except at tw r o 

 points where the lymph-vessels open into the veins (p. 329); 

 there some lymph is poured in and mixed directly with the 

 bLood. Accordingly everything which leaves the blood 



