188 PHYSIOLOGY OF MUSCLES AND NERVES. 



a spring against the wire, and replaces the slide. By 

 turning the disc the length of the inserted portion of 

 the rheochord is altered. 



The whole arrangement is shown more clearly in 

 tig. 48, which may at the- same time serve as a diagram 

 of the experiments with muscles and nerves, to which 

 we are now about to turn our attention. N r' r S is the 

 circular rheochord wire, through which the current of 

 the measuring apparatus passes in the direction of the 

 arrow ; yu, is a muscle, two of the points on the outer 

 surface of which, being connected with the multiplier, 

 afford a current, which is exactly compensated by that 

 portion of the current which branches off from the 

 rheochord at the points r and o. The particular length 

 o r of the rheochord wire at which this exact compen- 

 sation is accomplished, indicates according to the fixed 

 standard (the degree of compensation) the difference in 

 tension at the particular points on the muscle which are 

 tested. This length may be found by turning the round 

 disc, together with the platinum wire, until the mul- 

 tiplier no longer indicates any deflection. By means 

 of a magnifying glass, the length of the inserted wire, 

 from its commencement at o to the reel at r, can be 

 read off on a graduated scale. 



