ADVANCED EXPERIMENTAL PHYSIOLOGY 283 



another 10 grms. and repeat the process until 100 grms. or more are 

 extending the muscle. In the same way reverse the process and 

 remove the weights of 10 grms. one by one. If now the lower ends of 

 the vertical lines drawn by the fall and rise of the lever are joined, a 

 curved line will be formed, showing that the extension of the muscle 

 becomes less and less for each additional weight. Further, when all the 



Fio. 166. Curve of extensibility and elasticity of gastrocnemius. The figures on 

 the curve are weights in grms. Temp., 15 C. (A.P.B.) 



weights have been removed, the writing point will be below the original 

 zero line, showing an 'extension-remainder' (Fig. 166). It will also be 

 seen that the line corresponding to the elasticity of the muscle is a 

 flatter and more gradual curve than that corresponding to the extension ; 

 this is caused by the long continued load impairing the elasticity of 

 the muscle. 



Fio. 167. Elasticity curve of quiescent muscle. To be read from right to left. 

 The figures on the curve are for weights in grms. (M.S. P.) 



If the experiment be repeated on a piece of rubber band, the line join- 

 ing the lower ends of the vertical lines will be nearly straight, and little 

 or no 'extension-remainder' will be seen. Figs. 167, 168 show a com- 

 parison of the lines thus described for a muscle and piece of rubber 

 loaded from to 500 grms. and then gradually unloaded again. 



A contracted muscle is more extensible than a resting one. This is 

 of importance in the body; for, otherwise, a sudden x and powerful con- 

 traction of a muscle, trying to lift a heavy weight, would be liable to 

 rupture either the muscle itself, or its tendon, or the bones to which it 



