THE PRINCIPLES OF MYODYNAMICS. l5l 



(2.) The spring-scales are dynamometers : — 

 One is used to show the pressure of the joint 

 surfaces, one is used to show the force of the 

 contractinor muscle, and one is used to show the 

 resistance to be overcome by the movable bone. 

 That is, the dynamometers represent the power, 

 the weight and the fulcrum. (3.) Also select 

 two weights — one weighing one-half pound, 

 the other two pounds. When the two bars, the 

 screw-eyes, and the three spring-scales -are 

 properly put together, they constitute a my- 

 ometer. 



138. The first thing to do experimentally is 

 to resolve the force of the dynamometer repre- 

 senting a muscle into its rectangular compon- 

 ents. This may be done by the myometer. See 

 Fig. 28. Let S b be the short bar, and L B be 

 the long bar of the myometer. Let the dynam- 

 ometer P represent a contracting muscle, and 

 the dynamometer W represent the resisting 

 weight. The points of insertion of the screw- 

 eyes may be seen by an examination of the 

 figure. Some experiments may now be made : 



First. Let S c equal L c — that is, let the two 



