THE ARTERIES AND THE ARTERIAL CIRCULATION. 285 



Mr. Marey has illustrated these facts by an exceedingly ingenious 

 and effectual contrivance. He attached to the pipe of a small forcing 

 pump, to be worked by alternate strokes of the piston, a long elastic 

 tube open at the farther extremity. At different points upon this 

 tube there rested little movable levers, which were raised by the 

 distension of the tube whenever water was driven into it by the 

 forcing pump. Each lever carried upon its extremity a small pen- 

 cil, which marked upon a strip of paper, revolving with uniform 

 rapidity, the lines produced by its alternate elevation and depression. 

 Bv these curves, therefore, both the extent and rapidity of distension 

 of different parts of the elastic tube were accurately registered. 

 The curves thus produced are as follows : 



Fig. 93. 



('. KVKS OF THE A R T K R i A T, P r T, s A T i n s , as il 1 n*t ratf>d hv M. Marpy'n experiment. 1. Is'ear 

 the distending force. 2. At a distance from it. 3. Still farther removed. 



It will be seen that the whole time of pulsation is everywhere of 

 equal length, and that the distension everywhere begins at the same 

 moment. But at the beginning of the tube the expansion is wide 

 and sudden, and occupies only a sixth part of the entire pulsation, 

 while all the rest is taken up by a slow reaction. At the more 

 remote points, however, the. period of expansion becomes longer 

 and that of collapse shorter ; until at 3 the two periods are com- 

 pletely equalized, and the amount of expansion is at the same time 

 reduced one-half. Thus, the farther the blood passes from the heart 

 outward, ihe more uniform is its flow, and the more moderate the 

 distension of the arteries. 



Owing to the alternating contractions and relaxations of the heart, 

 accordingly, the blood passes through the arteries, not in a steady 

 stream, but in a series of welling impulses ; and the hemorrhage 

 from a wounded artery is readily distinguished from venous or 

 capillary hemorrhage by the fact that the blood flows in successive 

 jets, as well as more rapidly and abundantly. If a puncture be 

 made in the walls of the ventricle, and a slender canula introduced, 



