EXTENSIBILITY OF MUSCLE 55 



weight until ten or twelve have been added, moving on 

 the drum -5 cm. after each addition. The extension be- 

 comes less and less, and the lower extremities of the 

 lines traced by the fall of the lever are obviously points 

 on a curved line. Remove the weights in succession 

 turning the drum as before. The muscle does not return 

 to its original length, i.e. its extensibility is imperfect. 



4. Substitute for the muscle a strip of sheet india- 

 rubber, and test the extensibility of the rubber in exactly 

 the same way. Observe that each weight added stretches 

 the rubber an equal "amount and a line joining the ex- 

 tremities of the tracings is a straight one. 



5. Plot out on squared paper the curves of extensi- 

 bility. 



DEMONSTRATION. 

 The ergograph. 



