358 THE OUTGO OF ENERGY 



THE WORK DONE 



Influence of Load on Work done. In the 



tracings obtained in the experiments on page 341 

 with loads of 10 grams and upwards measure 

 the distance from the summit of each curve to 

 the abscissa. Calculate the gram-millimetres of 

 work done at 10, 30, 50, 70, and 90 grams, 



using the formula W= in which W is work 



m 



done, in gram-millimetres ; iv, the weight lifted 

 in grams, i. e. the weight of the scale-pan and 

 lever (about 12 grams) plus the weight put into 

 the scale-pan (the weight of the muscle itself 

 may be neglected) ; h, the height, in millimetres, 

 to which the load is lifted ; m, the magnification 

 of the lever. 



Write the results on the smoked paper. 



Note that within wide limits an increase in the 

 load increases the work done by the muscle. 



Absolute Force of Muscle. Secure the femur 

 of a gastrocnemius muscle preparation in a mus- 

 cle clamp and fasten the tendon to the rigid 

 muscle lever. After-load the muscle until it 

 just fails to lift the load when stimulated with 

 tetanizing induction currents. 



The load which neither extends a contracting 

 muscle nor allows it to shorten is a measure of 

 the " absolute force " of the muscle. 



