RESPONSE OF DIGESTIVE ORGANS 347 



sustained. In this connection it is suggestive that the digestive 

 organs should show so strongly marked a characteristic of 

 multiple response. It would thus appear, as already said, that 

 mechanical stimulation during ingestion of food gives rise to 

 the responsive reaction of secretion, evidenced electrically by 

 response of galvanometric negativity of the internal surface. 

 There then sets in the opposite phase, associated with the 



FIG. 213. Photographic Record of Multiple Responses in Stomach of 

 Frog to a Single Strong Thermal Shock 



Four parts are given of this long series, (a) Negative series ; (b) Alter- 

 nating negative and positive constituent responses ; (c ) Positive series ; 

 (d) Positive series. Note trend of base-line upwards in negative a, 

 and downwards in positive d. 



reversal of electrical response, probably indicating the ab- 

 sorptive process. This reversal of response, to galvanometric 

 positivity, may be the work of three different factors, which 

 may or may not be mutually dependent. In the first place, 

 we have seen that long-continued stimulation was apt of 

 itself, other things being equal, to give rise to a reversal of 

 response. Secondly, after secretion has reached its maxi- 

 mum, the empty mucous cells in contact with fluid would 

 naturally tend to reabsorb. And, lastly, we have seen that 

 an increase of internal energy, in whatever way produced, 



