INFLUENCE OF VER ATRIA ON CONTRACTION. 



175 



2. Influence of the Load on the Form of the Curve. 



(a.) Arrange an experiment with the pendulum myograph 

 as in Lesson XXXII., 1, using either a muscle-lever or a 

 crank-my ograph . 



(b.) Take a tracing with the muscle weighted with the 

 lever only. 



(c.) Then load the lever successively with different weights 



250 DV. 



Fig. 69. Pendulum Myograph Curves showing the Influence of the Load 

 on the Form of the Curve. 



(5 ... 20 ... 50 ... 70 ... 100 grammes), and in 

 each case record a curve and observe how the form of 

 the curve varies (Fig. 69). 



(d.) In each case record the abscissa and time curve with 

 the usual precautions. 



Fig. 70. Veratria Curve (Upper). Normal Muscle Curve (Lower). 



3. Influence of Veratria on Contraction. 



(a.) Destroy the brain of a frog, and inject into the 

 ventral lymph sac 10 minims of a freshly-prepared O'l per 

 cent, solution of veratria. 



