706 COMPARATIVE ELECTRO-PHYSIOLOGY 



natural current was reversed, owing to the greater relative 

 excitation induced at the glandular surface, which now 

 became relatively negative, to the extent of '0020 volt. 

 With the intact human tongue, further, I found that a 

 very strong responsive current was induced on excitation, 

 from the lower to the upper surface, thus showing that the 

 lower was the more excitable of the two. 



The response of digestive organs may now be passed in 

 review. In these, as in glandular organs, excitatory response 

 is supposed to take place by secretion. In connection with 

 this, it must be borne in mind that in the tissue of the 

 pulvinus of Mimosa, on the removal of the impervious skin, 

 excitation induces secretion of the contained fluid, which, 

 again, is re-absorbed on the cessation of excitation. We 

 know the pulvinus to be contractile, and may therefore 

 regard this secretion as an effect of contraction, causing 

 expulsion of water. Apart from the differential action of 

 the upper and lower halves of the organ, and the magnifying 

 petiolar index, the fundamental contractile action would, in 

 the case of Mimosa, as in others, have passed unnoticed. 

 This goes to show that it is not impossible that the phe- 

 nomenon of secretion through a permeable membrane may 

 be associated with excitatory contraction. In favour of such 

 continuity, it may be urged that tissues, hitherto regarded as 

 non-motile, have been shown to exhibit excitatory contrac- 

 tion. In digestion, as a whole, we have to recognise two 

 different processes, those, namely, of secretion, and of sub- 

 sequent absorption. Parallel to these, we find that the 

 electrical response of digestive organs exhibits phasic alter- 

 nations of negativity and positivity. 



It was shown that the pitcher of Nepenthe which may 

 be regarded as an open stomach affords us unique facilities 

 for the observation of the normal responses of digestive 

 organs. In experimenting with the animal stomach, the 

 specimen has to be cut open, in order to make the necessary 

 connections ; and, owing to the highly excitable character of 

 the organ, this gives rise to intense excitatory action, the 



