24 PHYSIOLOGICAL CHARACTERISTICS OF MUSCLE 



connected with a revolving drum, we get a simple muscle 

 curve (Fig. 19). The time required for a simple contraction 

 varies with the muscles of different animals, and also with 

 different muscles of the same animal. After the muscle is 

 stimulated (Fig. 19), an appreciable time elapses, the latent 

 period, before it contracts, which is about Moo second. Then 

 the muscle passes into the stage of contraction, during which 

 time the lever rises. Immediately it relaxes and elongates 

 and the lever again descends to the base line. The whole 

 contraction occupies about Mo second. 



FIG. 19. Simple muscle curve. (Halliburton.) 



Those factors which modify the character of a simple 

 muscle curve are, (a) the strength of the stimulus, (b) the 

 amount of the load, (c) the influence of fatigue, (d) the ef- 

 fect of temperature, and (e) the effect of veratrine. 



(a) A stimulus which is just strong enough to produce a 

 contraction is called a minimal stimulus. As the strength of 

 the stimulus is increased the amount of the contraction, 

 which is represented by the height of the curve, is increased. 

 This continues until a certain point is reached, the maximal 



