266 



PRACTICAL PHYSIOLOGY. 



[LIV. 



LESSON LIV. 



SUSPENSION METHODS FOB HEART GASKELL'S 

 HEART-LEVER AND CLAMP. 



1. GaskelTs Heart-Lever (Suspension Methods). 



(a.) This lever is extremely convenient (fig. 187). Expose the 

 heart of a pithed frog, ligature and divide the fraenum, tie a fine 



silk thread to the apex of 

 the ventricle, and attach the 

 thread to the writing-lever 

 placed above it. The lever 

 is kept in position by a thin 

 thread of elastic, which 

 raises the lever after the 

 contraction of the heart has 

 depressed it. 



(b.) Record the movements 

 on a drum moving at a 

 slow rate. Record time in 

 seconds. 



(c.) First the auricles con- 

 tract and pull down the 

 lever slightly, then the 

 greater contraction of the 

 ventricle pulls the lever 

 down further, and when the 



Fm 187. Showing the Arrangement of the Frog vpn f iT .i o lp r plavp? tViP Ipvpr 

 and Lever for a Heart-Lever, supported by a 7 er relaxes, I 



fine elastic thread. is raised by the elastic thread. 



Fig. 1 88 shows tracing ob- 

 tained when the heart is free and no clamp is applied. 



FIG. 188. Tracing of a Frog's Heart taken with Apparatus shown in Fig. 187. 

 H. Heart-tracing ; T. Time in seconds. 



A weak spiral spring may be used instead of the elastic thread. 



