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ESSENTIALS OF PHYSIOLOGY. 



Methods of measuring the Velocity of the Blood Flow. (1) 

 Ludwig's Stromuhr. This consists of two glass vessels A and B 

 connected at the top (fig. 61). On A is a mark c, the capacity of 

 the vessel below the mark being exactly known. The vessels are fixed 

 at their lower ends into a metal disc H, placed upon a similar disc N, 

 and capable of being rotated upon the latter through two right angles. 

 The openings a and b' in the upper disc fit exactly over those (a and b) 

 in the lower disc ; from these openings in the lower disc arise two 

 tubes F and G. The experiment is carried out as follows. A clip is 

 placed on an artery, which is then divided and connected at one end 



F G 



1 2 



FIG. 61. 1, Ludwig's stromuhr ; 2, Diagrammatic representation. 



with tube F, at the other with tube G. The tube and the vessel A, which 

 communicate with the proximal end of the artery, are filled with olive oil 

 up to the mark c, and the remainder of the apparatus is filled with 

 defibrinated blood. The blood is then allowed to flow through F into 

 A, thus driving the oil over into B and sending the defibrinated blood 

 into the peripheral end of the artery. As soon as the blood leaving 

 the artery reaches the mark c, the disc H is turned rapidly through 

 two right angles, and the blood flowing from the artery now drives the 

 oil back into A. When the oil again occupies its original position, the 

 disc is once more rotated through two right angles. This process is 

 repeated as often as necessary, the experiment being carried on for any 

 desired period ; clotting of the blood can be prevented by the previous 



