24 PHYSIOLOGICAL CHARACTERISTICS OF MUSCLE 



nected 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 3-^ 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 T \) 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 effect of temperature and 

 (e) the effect of veratrine. 



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

 traction 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 con- 

 tinues until a certain point is reached, the maximal stimulus, 



