182 GENERAL PKOPERTIES OF LIVING TISSUES 



limb going upwards, the other downwards. If 

 the muscle be severed between the forks, no 

 impulse started in one half of the muscle could 

 reach the other half, except by going up one 

 branch to the original axis cylinder and down 

 the remaining branch ; for it is known that the 

 nerve impulse does not escape transversely from 

 one axis cylinder to other neighboring ones. 



Remove a sartorius muscle with great care. 

 Split the muscle in the middle line for one third 

 of its length, beginning at the broad end, as in- 

 dicated in the diagram. Stimulate the muscle 

 fibres of the right segment mechanically, by 

 snipping the preparation with scissors in the 

 line a. Do not cut quite through the segment. 



Only the right half twitches. 



Repeat the stimulus by snipping in the line a r 



Again only the right half twitches. 



Stimulate in the line b. 



Both segments twitch, or at least some fibres 

 in each. 



Repeat at b r 



Both segments twitch again. 



2. The gracilis of the frog is divided into an 

 upper, shorter part and a lower, longer part by 

 a tendon (Fig. 44, /). Each axis cylinder in 

 the nerve N, on approaching the muscle, divides 

 into two branches, one of which goes to the 



