RESPONSE OF EPITHELIUM AND GLANDS 



319 



had become negative. The induced variation from the 

 original condition, in the present case, was from + '0013 

 volt to '0020 volt. It will thus be seen that any irritation 

 is liable to change the natural positivity of a highly excitable 

 glandular surface to negativity. The supposed similarities 

 between the ingoing responsive currents of frog's skin, and 

 the glandular surface of the stomach, are therefore not real. 

 That the two cases are quite different is proved indeed by 

 the fact that local stimulation of the surface of the skin 

 induces galvanometric positivity, whereas a similar stimulation 



Kthe glandular surface induces negativity. 

 In experimenting on animal tissues, it is therefore ad- 

 sable, wherever possible, to use intact specimens. The 

 numerous experimental difficulties with which we are in that 

 case confronted, may be overcome by the method of simul- 

 taneous and equi-alternating shocks which has been described. 

 How practicable this method has been 

 rendered will appear from the experi- 

 ments which I have yet to describe on 

 human subjects. 



We have seen that a protected sur- 

 i face is likely, other things being equal, 

 to be more excitable than an exposed 

 one. Partly owing to this fact, and 

 partly also to its richer possession of 

 imbedded glands, it appeared to me 

 probable that the inner surface of the 

 armpit would prove electrically more FlG 

 excitable than a corresponding area, on, 

 say, the upper and outer surface of the 

 same shoulder. In the records which I 

 ucceeded in obtaining (fig. 194), this 

 pposition was fully borne out. Equi-alternating shocks of 

 e second's duration were applied at intervals of one minute, 

 nd the direct effect photographically recorded. The re- 

 Iting responses were found to be ingoing as regards the 

 rmpit, thus proving that that surface was the more excitable. 



194. Photographic 

 Record of Electrical 

 Responses of Intact 

 Human Armpit 



Responsive current from 

 armpit to shoulder. 



