ELEMENTARY EXPERIMENTAL PHYSIOLOGY 35 



CHAPTER VI. 



THE CONDITIONS WHICH AFFECT SINGLE MUSCULAR 

 CONTRACTIONS CONTINUED. 



(d) Load. In order to study the effect of variations in load upon 

 a single muscular contraction, the apparatus is arranged for stimu- 

 lating the muscle by a single maximal induction-shock, the drum 

 being placed as a key in the primary circuit and arranged to rotate at 

 a fast rate. Make a gastrocnemius-sciatic or hyoglossus preparation. 



FIG. 40. The effect of load upon the contraction of the gastrocnemius muscle (A P.B.) 



FIG. 41 is the continuation of the experiment in Fig. 40. Single contractions of the 

 gastrocnemius with different loads. The figures on the curves represent the weights 

 in grms. hung at the axis of the lever ; actual load on muscle was in each case one- 

 fifth. Magnification, 5. Temp., 12' C. (A.P.B.) 



Record a single contraction of the muscle weighted only by the lever, 

 mark the latent period and draw a base-line. Then hang on to the 

 lever near its axis weights increasing by 20 grams at a time, and 

 for each addition of weight record a contraction. The base of the 

 stand carrying the myograph should not be moved during the experi- 

 ments, but the curves should be superimposed as in Figs. 40 and 41. 

 Each increase of weight stretches the muscle, consequently it is 



