444 MANUAL OF PHYSIOLOGY. 



If a tracing be drawn showing the extending effect of a series 

 of equal weights attached to a fresh muscle, it will be found that 

 a great difference exists between it and a similar record drawn by 

 inorganic bodies or an elastic band of rubber. 



When a weight is applied to a muscle, it does not immediately 

 stretch to the full extent the weight is capable of effecting, but a 

 certain time, which varies with circumstances, is allowed for its 

 complete extension. The rate of extension is at first rapid, then 

 slower, until it ceases. As a muscle loses its powers of contrac- 

 tion from fatigue, it becomes more easily extended. Dead muscle 



FIG. 180. 



1. Shows graphically the amount of extension caused by equal weight 

 increments applied to a steel spring. 2. Shows graphically the amount of 

 extension caused by equal weight increments applied to an india-rubber 

 band. 3. The same applied to a frog's muscle. Showing the decreasing 

 increments of extension, the gradual continuing stretching, and the failure 

 to return to the abscissa when the weight is removed. 



has a greater but less perfect elasticity than living, i.e., it requires 

 greater force to stretch it, but does not return so perfectly to its 

 former shape. The importance of the elastic property of muscle 

 in the movements of the body is noteworthy. The muscles are 

 always in some degree on the stretch (as can be seen in a frac- 

 tured patella, the fragments of which remain far apart and cause 

 the surgeon much anxiety), and brace the bones together like a 



