8o ANIMAL ELECTRICITY. LECTURE IV. 



the ulnar nerve at the back of the elbow ; when the 

 knob is felt to be comfortably applied, the current, 

 directed so as to have its kathode at that spot, is 

 gradually increased, the effect of its make and break 

 being tested for occasionally. A strength is reached 

 at which each make of the current gives a sharp flexor 

 movement of wrist and fingers — i.e., the kathode ex- 

 cites at make, or, otherwise, the make excitation is 

 kathodic. Now the current is reversed, so that the 

 kathode pressed down on the nerve is changed to an 

 anode, and the current is made as before at the key, as 

 you hear — but, as you see, without producing any effect ; 

 the anode does not excite at make. But neither does 

 it excite at break — at least at this rather low current- 

 strength. The current must be increased before any 

 break effect appears with the anode over the nerve, 

 and then there is also a make effect — which apparently 

 contradicts the statement that the anode does not excite 

 at make — that on the contrary it quells excitation. 

 The contradiction is apparent and not real, yet, as 

 regards the course of our main channel of thouoht, 

 any full consideration of the point would lead us 

 astray. Let me then say rapidly that in this em- 

 bedded nerve, current, having a fairly narrow way in 

 (= anode), just under the electrode, has also a com- 

 paratively broad way out (= kathode) into the sur- 

 rounding tissues, at some little distance from the actual 

 electrode. The make effect is due to this extra-polar 

 kathode — please do not regard it further ; it is a com- 



