186 



PHYSIOLOGY OF MUSCLES AXD ^'ERVES. 



difference in tension between R and S can be altered 

 by changing the position of S, the slide S may be 

 placed in such a position that the two influences exactly 

 balance each other, or, in other words, in such a position 

 that the multiplier indicates no deflection. Thus it is 

 evident that 



S - B 



Difference in tension at tlie 

 two points of tlie rlieochord. 



b - 



a 



= 



Difference in tension at 

 the two points of the con- 

 ductor. 



m ^ - R = h - 



a 



the difference, that is, of the tension between 6 and a 

 is equal to the difference of tension between B and K. 



Fig. 47. Du Bois-Rkymond's round cumim^nsator. 



The latter is expressed in millimetres, each of which 

 indicates a certain constant amoiint when a definite 

 rheochord wire is used, and when the current which is 

 conducted through the latter is of a definite strength. 

 To facilitate measurements of this kind, du Bois- 



