34 THE PHYSIOLOGY OF MUSCLE AND NERVE. 



contracture when compared with that of the simple contraction indicates the 

 possibility that two different contraction processes may take place in muscle, 

 one involving the state of tone and, therefore, the length and hardness of 

 the muscle, the other controlling the quick changes in length. This suggestion 

 has been made by a number of authors* on various grounds. It has been 

 suggested by some that there are two different contractile substances in mus- 



Fig. 15. — Effect of repeated stimulation; complete curve, .showing late contracture. 

 The muscle was stimulated by inductioH shocks at the rate of 50 per minute. The separate 

 contractions are so close together that they can not be distinguished. 



Fig. 16. — Effect of repeited stimulation, curve showing no contractureor very little. 

 The muscle was stimulated by induction shocks at the rate of 50 per minute. A very 

 slight contracture is shown in the beginning, but subsequently the contractions show 

 only a diminished extent, the rate of relaxation remaining apparently unchanged. 



cle, one giving the usupI quick contraction, known as a "twitch," the other 

 the slower contraction, which exhibits itself as tone or contracture.! 



* See especially Uexklill, "Zentralblatt f. Physiologic," 1908, 22, 33; also 

 Guenther, "American Journal of Physiology," 1905, 14, 73. 



t loteyko, "Travaux du laboratoire de Physiologic," Institut Solvay, 1902, 

 5, 229. 



