The electrical phenomena accompanying sécrétion. ]2f) 



of the chorda, and particularly after repeated excitation, the amount 

 of the current of rest is diminished. This however is by no means a 

 constant result, and may not be of much importance; at the same 

 time it deserves mention since when present it is well-marked. The 

 sympathetic does not produce the same effect. Again as before men- 

 tioned the current of rest on the whole diminishes in amount during 

 an experiment, particularly if the observations are carried on for 

 several hours, and since it is precisely in these cases that the chorda 

 has been most frequently excited, this diminution may in part be due 

 to the effects of nerve -excitation. 



Electrical phenomena ohserved on stimulation of the sympathetic. — 

 In all cases excitation of the sympathetic causes well marked changes 

 of potential, which are very different from those produced on exci- 

 tation of the chorda. The latter, as we have seen, have a very short 

 latent period, are readily abolished by atropine, and are of such a 

 nature as to cause the outer surface of the gland to become negative, 

 occasionally followed by the outer surface becoming positive. Exci- 

 tation of the sympathetic, however, produces, after a very long latent 

 period, an electrical effect very refractory as regards the action of 

 atropine on it, and of such a nature that the outer surface of the 

 gland becomes positive to the hilus. Not only is the latent period of 

 this sympathetic variation very long, but the course of the variation 

 is very slow, reminding one of the results obtained on the tongue of 

 the frog by excitation of the glossopharyngeal *■). 



Further the amplitude of the variation is much less than that of 

 the chorda, in fact the sympathetic variation is generally a small one, 

 a movement of the spot of light over from 50 — 100 divisions of the 

 galvanometer- scale being the whole result even of a tolerably strong- 

 stimulus. Thus on excitation of the sympathetic with the secondary 

 coil at 8, the deflection of 62 was obtained, whereas in the same dog, 

 the deflection produced by excitation of the chorda with the coil at 

 10 reached a maximum which was more than 20 times as great as 

 in the case of sympathetic- excitation. The rapidity of the variation 

 in the case of the sympathetic is also much less and the latent pe- 



*) Hermann and Luchsinger, Pflüger's Archiv, XVII. 



