340 THE OUTGO OF ENERGY 



are similar in form, but different in duration. 

 The curve of thickening is shorter by the differ- 

 ence between the time taken by the contraction 

 wave to pass over the single cross-section, on the 

 one hand, and the whole length of the muscle on 

 the other. 



An extirpated muscle is apt to remain short- 

 ened after contraction. To bring muscles back 

 to their original length it is usually necessary to 

 weight them, or as in the body to submit 

 them to the pull of antagonists. Even the 

 weighted muscles may return very slowly and 

 imperfectly to their normal length. This con- 

 tracture, as it is termed, is seen especially in 

 strong direct stimulation, in poisoning with vera- 

 trine, and as death comes on. Contracture is 

 not the result of fatigue, for when the muscle 

 is repeatedly stimulated contracture diminishes, 

 instead of increasing. During contracture, the 

 irritability of the muscle for stimulation through 

 the nerve is diminished. 



Relation of Strength of Stimulus to Form of 

 Contraction Wave. Fasten the femur of a gas~ 

 trocnemius preparation in the muscle clamp and 

 attach the Achilles tendon to the muscle lever 

 with a fine copper wire the end of which should 

 be carried to the binding post on the handle of 

 the lever. Connect this post and that on the 



