66 



PHYSIOLOGY 



CHAP. 



from the weight, when it begins to relax, and the work done in 

 contraction is utilised ; when the break is removed, the work done 

 is cancelled and converted into heat when the muscle relaxes. 



Fick's results confirmed Beclard's hypothesis. In a series of 

 contractions produced by stimuli of uniform strength, while the 

 muscle is performing useful work, less heat is evolved than in a 



h 



FIG. 40. Fick's Arbeitssammler, by which the muscle is loaded with a weight during contraction, 

 and unloaded during relaxation. While contracting, the muscle (frog's gastrocnemius) lifts 

 the lever r rj, Avftich in itself offers little resistance, as it is almost balanced by the small 

 counterpoise I. But owing to the support h, which presses on the edge of the graduated disc 

 m in (which revolves round the same axis as the lever), the disc turns as the lever rises, along 

 with the concentric pulley that carries the thread to which the weight is attached. The 

 muscle is thus loaded during contraction, and lifts the weight to a height that can be exactly 

 measured by the degree of rotation of the disc shown on the scale j. In relaxing, the muscle 

 is freed from its load, because the disc and pulley cannot drop back owing to the stop hi. 

 The weight remains up, and the lever sinks to its original position owing to the slight pre- 

 ponderance of arm r over arm r\. At each succeeding contraction the weight is lifted higher, 

 so that from the total rotation of the disc it is easy to calculate the total sum of work per- 

 formed by the muscle in a given number of contractions. When the stop hi is removed from 

 the edge of the disc, the apparatus can be used as a simple isotonic lever. At each contraction 

 the muscle rotates the disc and lifts the weight ; but at each successive relaxation the work 

 done is cancelled, because the disc retracts with the lever owing to the pull of the weight. 



second series of uniform contractions, produced by stimuli of the 

 same strength, in which the muscle performs no useful work. 



The later work of Danilewsky, Blix, and Chauveau leads to the 

 same conclusion. 



On comparing the heat developed by a series of maximal 

 muscular contractions in a given time without useful work, with 

 that developed by the same muscle in the same time with maximal 



