s 



RESPONSE OF DIGESTIVE ORGANS 333 



glands. The visible changes which occur under stimulation 

 in these three types of tissues would thus appear to differ 

 only in degree. 



We may now turn more especially to the question of the 

 electrical reactions of the digestive mucosa. As regards the 

 natural current of rest, we have seen that Rosenthal and 

 others found that this current was ingoing that is to say, 

 the mucous layer was negative, as compared to the muscular 

 coat of the stomach. Biedermann had also noticed a strong 

 current of rest between the glandular surface of Drosera and 

 the stalk.- But it will be shown that the glandular coat of 



e stomach is more excitable than the muscular layer. 



ence we should have expected that the natural current of 

 rest would have been from the less excitable to the more 

 excitable, the mucous layer in a state of rest being thus 

 relatively galvanometrically positive. The opposite direc- 



>n of the current which has been observed, would rather 

 pear to be ascribable to the excitatory after-effect of pre- 

 ration. I have already described how the glandular foot 

 the snail, under conditions of perfect rest, is galvano- 

 metrically positive. But the excitation caused by prepara- 

 tion renders this highly excitable glandular surface negative 

 That the fact of cutting open the stomach, to make the 

 experimental preparation, similarly, would cause intense 

 excitation with galvanometric negativity, was to have been 

 expected. I shall be able, indeed, to show, by means of 

 experiments to be described presently, that the shock con- 

 sequent on this preparation is to give, not one, but a pro- 

 longed series of multiple electrical responses. 



I have almost invariably found, in making electrical 

 contacts after section, with the inner and outer surfaces of 

 frog's stomach, that the multiple responses caused by section, 

 persisted for more than an hour ; and until these had 

 subsided no fresh experiment could be undertaken, to 

 obtain records of the response of the stomach to external 

 stimulus. I have also found that many of these frogs were 

 in the habit of swallowing stones and pebbles, the persistent 



