ELEMENTARY EXPERIMENTAL PHYSIOLOGY 



59 



The lever is provided with a long light straw. In place of the weight 

 a fine rubber thread may be attached to the lever. One end of the 



FIG. 55. Suspension method of recording the contraction of the frog's heart, with 

 use of rubber thread as a spring. 



rubber thread is tied on to the short arm of the lever, and the other end 

 is pinned to the cork of the myograph. By making the rubber thin 



FIG. 56. Contractions of the frog's heart. A = auricular, V = ventricular con- 

 traction. The time is marked in seconds. The curve should be lead from left 

 to right. (L.H.) 



