ELASTICITY OF MUSCLE. 177 



length, so that its elasticity is said to be very perfect. The 

 hyperbolic curve obtained shows further that the increase in 

 length is not directly proportional to the weight; but it 

 diminishes as the weights increase. 



(c.) Repeat the same observation with a thin strip of 

 india-rubber. In this case equal increments of weight give 

 an equal elongation, so that a line joining the apices of the 

 vertical lines drawn after each weight is a straight line. 



2. The Extensibility of Muscle is Increased during Contraction, 

 its Elasticity is Diminished. 



(a.) Arrange a muscle in a moist chamber, connecting it 

 to a lever to record on a drum, and adjust an interrupted 

 current to stimulate the muscle, either directly or indirectly. 



(b.) Load the lever with 50 grammes, and in doing so 

 allow the drum to move slowly. Remove the load and 

 observe the curve obtained. 



(c.) Tetanise the muscle, and while it is contracted to its 

 greatest extent, again load the lever with 50 grammes while 

 the drum is in motion, and remove the load. Observe the 

 curve. 



(d.) Compare the two curves. The second curve will, of 

 course, begin higher, but notice that its absolute descent is 

 greater than the first curve, and that it does not rise to the 

 horizontal again. 



(e.) It is better to begin the experiment with the drum 

 stationary, and then to record the tracing with the drum in 

 motion. 



(/.) A better curve is obtained by using a long counter- 

 poised lever attached to the muscle, which writes on a very 

 slow-moving drum. A weight is made to travel along the 

 lever by means of two pulleys with an endless string. 



