544 A TEXTBOOK OF PHYSIOLOGY 



tracting muscles are those rich in sarcostylcs, the slowly contracting 

 muscles those containing abundant sarcoplasm; many muscles are 

 mixed. It has been suggested that, when the number of sarcostyles 



FIG. 280. 



The upper curves show the latent period and movements of two levers on muscle 

 at 15 C., the lower curves at 5 C. It will be seen that the latent period is 

 shorter at 15 C. than at 5 C., also that the rate of conduction given by the dif- 

 ference in the latent periods is quicker at 15 C. than at 5 C. (V. J. Woolley.) 



are not greatly in excess of the amount of sarcoplasm, the muscle 

 curve may show two summits the first due to contraction of the 

 sarcostyles, the second due to contraction of the sarcoplasm. This is 



FIG. 281. Ti-E EFFECT OF LOAD UPON THE CONTRACTION OF THE GASTROCNE.MII s 

 MUSCLE. (A. P. Bcddard.) 



the explanation sometime3 afforded of the curve given by the vera- 

 trinized muscle (Fig. 27L). It is also suggested that the slow response 

 of a fatigued muscle may be a response of the sarcoplasm after the 

 quickly responding sarcostyles have ceased to respond. For example, 



