THE CHANGE IN FORM 335 



The period is shorter at high temperatures than 

 at low, with maximal break induction currents 

 than with make induction currents, with break 

 induction currents than with closure of the gal- 

 vanic current. Changing the load of the muscle 

 is without effect on the latent period. 



When the muscle is stimulated through its 

 nerve the latent period is longer by about 0.002 

 sec. than when the electrodes are placed on the 

 muscle itself (Bernstein), due allowance being 

 made for the time occupied by the passage of 

 the nerve impulse along the trunk of the nerve 

 from the point of stimulation to the muscle. The 

 additional time is taken perhaps in the passage 

 of the impulse through the end plate into the 

 contractile substance. 



Grutzner has shown that the striated muscle 

 fibres, particularly of vertebrates, differ in their 

 histological elements. Some are rich in sarco- 

 plasm, and when seen by transmitted light appear 

 cloudy and granular ; others have less sarcoplasm 

 and are relatively translucent. This difference 

 in structure is associated with a striking differ- 

 ence in the character of the contraction. The 

 muscles composed chiefly of turbid fibres contract 

 slowly, while "clear" muscles contract rapidly 

 (compare page 178). Thus in the rabbit the 

 duration of the contraction of the red soleus 



