REVIEW OF RESPONSE OF ANISOTROPIC ORGANS 707 



after-effect of which is necessarily to reverse the normal 

 current of rest. With a pitcher of Nepenthe in a fresh 

 condition, the natural current of rest is from the outer to 

 the inner, the responsive current being in the opposite 

 direction, and the glandular surface, on simultaneous exci- 

 tation of the two, becoming galvanometrically negative 

 (fig. 203). Digestive organs, moreover, tend to -exhibit 

 multiple responses, the response to a single strong stimulus, 

 say thermal, or of mechanical section, consisting, whether in 

 animal or vegetable organs, of a series that may persist for 

 nearly an hour (figs. 206, 209, and 213). When the pitcher 

 of Nepenthe contains a large number of captured flies, that is 

 to say, when it has been subjected to long-continued stimu- 

 lation, it exhibits a phasic change, the responses now 

 becoming reversed to positive (fig. 205). This, as pointed 

 out above, is probably significant of absorption. In Drosera, 

 the normal response of the glandular surface is by induced 

 negativity, but on long-continued stimulation, this is reversed 

 to positivity (fig. 208). 



In the animal stomach, the observed current of rest is 

 generally from the glandular to the non-glandular surface. 

 From the fact that the skin of the toad, which is also 

 possessed of imbedded glands, gives a current of rest from 

 the outer surface to the inner, it has been supposed that the 

 mucous coat of the stomach of the frog had the same electro- 

 motive reaction as its outer skin. That this, however, is not 

 the case is seen from the fact that on excitation the skin 

 becomes galvanometrically positive, while the mucous mem- 

 brane of the stomach becomes galvanometrically negative. 

 The observed current of rest in the stomach would appear, 

 from Nepenthe, to be, not the natural current of rest, but the 

 reversed current, due to the excitatory effect of preparation. 

 The normal effect of excitation in the stomach, I uniformly 

 find, in such different instances as frog, gecko, and tortoise, to 

 be by galvanometric negativity of the mucous surface (figs. 

 210, 211, and 212). On applying a strong thermal stimulus 

 to the stomach of frog, I obtained an interesting series of 



z z 2 



