300 



ELEMENTARY PHYSIOLOGY 



LESS. 



When the nerve is stiniuhited by a stimulus which 

 lasts as short a time as possible, as, for instance, by the 

 momentary electric current often called an induction 

 shock, the following changes take place in the muscle. 



Fio. 90.— A Muscle Nerve Prkparatkin. 



TO, the rmiscle, gastrocnemius of frog ; np.f, lower cud of spiual column ; 

 n, the sciatic nerve, all the br.anches being out away excepting that 

 supplying the muscle ; /, the femur ; cl. a clamp to hold the femur ; t.a, 

 Achilles tendon. 



(i) It becomes shorter and thicker, lifts the weight 

 attached to it and then relaxes, allowing the weight to 

 fall again. The shortening and relaxing takes place very 

 rapidly, the whole px'ocess occupying rather more than 

 ^ of a second. 



