168 EXPERIMENTAL PHYSIOLOGY. 



(c.) Use different weights 5 20 50 grammes and 

 observe how the form of the curve varies on increasing 

 the weight attached to the lever. 



11. After-load. In the crank-myograph, under the lever is a 

 screw on which the horizontal arm of the bell-crank rests (Fig. 

 62, a), so that the muscle is loaded only during its con- 

 traction. 



12. Interrupted Current. If instead of single shocks, the induc- 

 tion apparatus be so arranged that Neef's hammer is in action, 

 then on stimulating the muscle or nerve, tetanus is obtained 

 (Lesson XXVIII, 3), and the curve of a tetanised muscle re- 

 corded. 



LESSON XXXII. 



ANALYSIS OF A MUSCULAR CONTRACTION 



-PENDULUM MYOGRAPH SPRING 



MYOGRAPH TIME-MARKER- 



DEPREZ' SIGNAL. 



1. Muscle Curve by the Pendulum Myograph. 



(a.) Cover the oblong glass plate with glazed paper, smoke 

 its surface, and fix it to the pendulum. The plate must be 

 so adjusted that the pendulum on being set free from the 

 "detent" (Fig. 63, C) shall be held by the catch " (0). 

 Test this. 



(b.) Arrange the induction apparatus for single shocks as 

 in Fig. 63, but shor^circuit the secondary circuit, inter- 

 posing in the primary circuit the trigger-key or knock -over 

 key of the pendulum myograph (Fig. 63, K'). 



