172 



Dr. A. D. Waller. 



made upon a freshly killed animal, affords a very convenient means of 

 class-demonstration of the fundamental fact. The response is elicited 

 by stimulation of the sciatic nerve after the latter has ceased to pro- 

 voke muscular contraction, and can then be most conveniently demon- 

 strated (and recorded) without resort to the curarisation and artificial 

 respiration necessary in the case of the living animal. The method 

 and its results will be made sufficiently apparent by the following 

 experiments and figures : 



Experiment 1 . Electrical Response of the Skin to Indirect Excitation 

 through the Sciatic Nerve. 



Cat decapitated -Both sciatics exposed and cut Large pad of each 

 hind foot led off to galvanometer by unpolarisable electrodes Tetanic 

 excitation of peripheral end of one or other sciatic for 5 seconds at 

 intervals of 5 minutes Berne coil at 1000 units supplied by two 

 Leclanches. 



Deflection + signifies that the skin of the right side is electro- 

 positive, i.e., that it is traversed by an ingoing current (directed from 

 left side to right through the galvanometer). 



Remarks. 



Muscles contract. 



Do. 



Do. 



Do. faintly. 

 No contraction. 



Do. 



Do. 



Do. 



Do. 



The effect of excitation was thus in each instance an ingoing current 

 of the skin of the excited side. 



Experiment 2. Similar Experiment. Excitation of Right Sciatic at 



Time, 

 mins. 



20 



30 



40 



50 



60 



70 



Intervals of 10 minutes. 

 Deflection. Remarks. 



+ 0-0050 

 + 0-0045 

 + 0-0035 

 + 0-0020 

 + 0-0005 

 Nil 



Faint contraction. 

 No contraction. 



Do. 



Do. 



Do. 



