THE ARTERIES AND THE ARTERIAL CIRCULATION. 289 



mingled, current shooting forward with increased velocity at every 

 cardiac pulsation. Volkmann, in Germany, has determined, by a 

 very ingenious contrivance, the velocity of the current of blood in 

 some of the large sized arteries in dogs, horses, and calves. The 

 instrument which he employed (Fig. 94) consisted of a metallic 

 cylinder (a), with a perforation running from end to end, and cor- 

 responding in size with the artery to be examined. The artery 

 was divided transversely, and its cardiac extremity fastened to the 

 upper end (b) of the instrument, while its peripheral extremity was 



Fig. 94. 



Fig. 95. 



VOI,KMAK'S APPARATUS for measnring the rapidity of the artorlal circulation. 



fastened in the same manner to the lower end (c). The blood 

 accordingly still kept on its usual course ; only passing for a short 

 distance through the artificial tube (a), between the divided extremi- 

 ties of the artery. The instrument, however, was provided, as shown 

 in the accompanying figures, with two transverse cylindrical plugs, 

 also perforated ; and arranged in such a manner, that when, at a 

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