352 THE OUTGO OF ENERGY 



thus be entirely out of the way. The steel spring 

 shown upon the left of Fig. 60 may then be turned to 

 the right to bring its wire hook into the opening 

 through which the scale-pan is reached. The scale- 

 pan may then be attached to this isometric spring and 

 the spring empirically graduated. When the gradua- 

 tion scale has been written, the milled screw that 

 holds the isometric spring upon the left-hand post 

 (Fig. 60) may be loosened, the spring turned with the 

 hook up, and the screw made fast again. The lower 

 end of the muscle may now be attached to the 

 hook upon the spring and an isometric curve written. 



The screw clamp holding the muscle clamp is 

 insulated. A binding post upon the muscle clamp, 

 and another binding post upon the right-hand post 

 supporting the axle of the lever, allow direct stimula- 

 tion of the muscle. 



This lever serves especially well for the double 

 abductor preparation of Fick, consisting of the semi- 

 membranosus and gracilis of both sides. 



Isometric Contraction.- Invert the spring. 

 Fasten the femur of a gastrocnemius preparation 

 in the muscle clamp, and the Achilles tendon to 

 the spring. Connect the binding posts on the 

 lever and the clamp with the secondary coil of the 

 inductorium, arranged for single maximal induc- 

 tion currents. Let the drum revolve at a rapid 

 speed. Stimulate the muscle with a maximal 

 break current. 



