THE CHEMISTRY OF MUSCLE. 71 



of the catgut will cause it to shorten, owing to the imbibition of 

 more water. When the current is broken the catgut cools and 

 relaxes slowly. Records may be obtained in this way which are 

 altogether similar or identical with those given by a strip of plain 

 muscle when stimulated (see Figs. 27 and 28). The model may be 



Fig. 28. Imitation of incomplete tetanus by the artificial muscle. The time and 

 duration of the successive heatings are indicated by the breaks in the lower line. Each 

 such heating causes a separate contraction, and these contractions are summated as in the 

 tetanic contraction of muscle. 



used to show the effect of temperature upon the extent and dura- 

 tion of the contractions, the effect of variations in strength of 

 stimulus as expressed in the amount of current used, the summation 

 of successive stimuli, etc. Under all of these conditions it imitates 

 closely the behavior of plain muscular tissue. 



