346 PEACTICAL PHYSIOLOGY 



excitatory wave travels by muscle and not by nerve from chamber 

 to chamber. 



Gaskell's Clamp and the Effect of Heat on Sinus and Ventricle. 

 The contraction of the auricle and ventricle are registered by means of 



FIG. 226. - Record of the contraction of auricle and ventricle (toad) by the use of 

 Gaskell's clamp and levers. The upper tracing is the auricle and here the contraction 

 is represented by the down-stroke. The time is marked in seconds. (L.H.) 



two levers which are attached by means of threads to the apex of the 

 ventricle and auricle respectively ; the one lever is pulled downwards 

 against an elastic spring and the other upwards. The heart is held 

 fast by means of a screw clamp in the auriculo-ventricular groove. 1 The 

 clamp is provided with a fine screw, which can easily be adjusted so as 

 to hold the heart firmly without injuring the tissue (Gaskell). In this 

 way the contractions of auricle and ventricle are registered separately. 

 Take a thick copper wire, bent into a hook at one end, and place the 

 hook round the sinus. Warm the other end of the wire in a flame. 



1 A screw clip, to the bars of which cork wedges are fastened, wilf do for the 

 clamp. See Fig. 207. 



