RESPONSE OF ANIMAL AND VEGETAL SKINS 



305 



a supposition seemingly supported by Rosenthal's discovery, 

 already referred to, that an apparently similar ' ingoing ' 

 current was to be observed in the mucous coat of the frog's 

 stomach. Against this may be urged the conclusion, to 

 which Hermann drew attention, that the skin glands are nor- 

 mally nearly closed to the external surface, and cannot there- 

 fore have any external galvanic relation. There are, moreover, 

 other arguments. First, a similar current is observed in the 

 case of grape-skin, where there is no special glandular layer. 

 Second, the specific response of a glandular surface is 



6 P.M. 



9 P.M. 



3 A.M. 6 A.M. 



FIG. 185. Continuous Photographic Record of Autonomous Pulsation of 

 Desmoditim gyrans from 6 P.M. to 6 A.M. 



The lower record is in continuation of the upper. Note phasic variation. 



definite, and is by galvanometric negativity, whereas the 

 response of the outer surface of frog or grape skin on 

 excitation is by galvanometric positivity. And, thirdly, we 

 shall see that the current observed in the mucous membrane 

 of stomach is most probably not the natural current of rest, 

 but the excitatory after-current. 



It will be remembered, however, that we have always 

 found the natural current to flow 'in the tissue from the less 

 to the more excitable, and the current of response in the 

 opposite direction. In the skin, owing to physiological and 



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