ANIMAL ELECTRICITY. LECTURE IV. 



97 



cold-blooded and warm-blooded animals respectively, 

 and I will bring this group of introductory considera- 

 tions to their conclusion by a cursory demonstration 

 of this contrast— upon the nerves of a frog and of a 

 kitten respectively — laying them in turn upon two pairs 

 of electrodes by which polarising current is led into 

 the nerve and extrapolar current is led out to the 

 galvanometer. 



With the frog's nerves the anodic extrapolar effect 

 (to the right) is comparatively large, the kathodic 



0*5 volt 



Fig. 43 (2383). — Extra-polar ( = " electrotonic ") currents of kitten's nerve. 

 produced by polarising currents of increasing strength from 0*5 to 2*0 volts. (The 

 standard deflection by O'ooi volt had a value of 40 mm., so that e,g: the A. and 

 K. currents at 2 volts have an E.M.F. of about 0*0007 volt). 



extrapolar effect (to the left) is comparatively small. 

 These extrapolar effects are not due to current-escape, 

 for they are, as you see, completely abolished by 

 pinching the nerve between the two pairs of elec- 

 trodes. 



With the kitten's nerve the anodic and kathodic 



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