46 ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



work (W) performed by the muscle each time equals the weight (w) 

 multiplied by the height to which it has been lifted (fi). The work of 

 the muscle is expressed in gram-millimeters. 



9. Addition of Work. In order to determine the amount of work 

 accomplished by a muscle in a given period of time we make use of an 

 instrument which is known as a work-adder (Fick). Adjust this 

 instrument upon the edge of the table, allowing the weight (10 grams) 

 suspended from its pulley to touch the floor. Fasten the femur of a 

 gastrocnemius preparation in the clamp and attach its tendon to the 

 lever of the work-adder. Apply the electrodes to the upper part of 

 the muscle, and stimulate it at the rate of once in every second during 

 a period of thirty seconds. The individual make and break shocks 

 may be put in successively, i. e., it is not necessary to short-circuit the 

 makes. Compute the work performed during this period by multi- 

 plying the weight by the height to which it has been lifted (W = wh). 



Annotation. In short-circuiting the make, the cross-bar attached to the rods 

 of the secondary coil is moved downward into its position of closure. The current 

 is then made, but cannot reach the muscle because it selects the route of least re- 

 sistance across the bar. Now open this bridge and break the circuit. The break 

 shock may be short-circuited by simply closing the bridge directly after the make 

 has been allowed to enter the muscle. 



