132 GENERAL PROPERTIES OF LIVING TISSUES 



A 







c 



/fa. 



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Fig. 37. 



cal anodes on both sides of the negative electrode. 



Thus both anodal and cathodal stimulation take 



place, whichever electrode rests over the nerve. 



It is therefore incorrect to speak of ascending 



and descending currents in the case of nerves 

 stimulated in situ. It should be 

 pointed out, too, that the density 

 of the current is greater on the 

 side of the nerve nearer the 

 electrode than on the more deeply 



placed side cut by current lines already rapidly 



diverging. 



With these facts in mind, we may compare 



the polar stimulation of human nerve with the 



law already determined for the isolated nerves 



of the frog (page 115). 



The Brass Electrodes. The brass electrodes, 

 used chiefly for the stimulation of human muscles 

 and nerves, are two in number: 

 an "indifferent" electrode, con- 

 sisting of a brass plate, 3x6 

 cm., with binding post, and 

 a " stimulating " electrode, of 

 brass rod, 6 cm. long, ringed 

 at one end and provided at the 

 other with a binding post. Be- 

 tween these the rod is insulated with rubber tubing. 

 - The electrodes should be covered with cotton wet 



Fig. 38. 



