CHAPTER XXIV 



RESPONSE OF DIGESTIVE ORGANS 



Consideration of the functional peculiarities of the digestive organs Alternating 

 phases of secretion and absorption Relation between secretory and con- 

 tractile responses. Illustrated by (a) preparation of Mimosa ; (b) glandular 

 tentacle of Drosera- -General occurrence of contractile response True current 

 of rest in digestive organs Experiments on the pitcher of Nepenthe Three 

 definite types of response under different conditions Negative and positive 

 electrical responses, concomitant with secretion and absorption Multiple 

 responses due to strong stimulation Response in glandular leaf of Drosera 

 Normal negative response reversed to positive under continuous stimulation 

 Multiple response in Drosera Response of frog's stomach to mechanical 

 stimulation Response of stomach of tortoise Response of stomach of gecko 

 Multiple response of frog's stomach, showing three stages negative, 

 diphasic, and positive Phasic variations. 



HAVING now dealt with the responsive characteristics of the 

 skin, epithelium, and glands, alike in plant and animal, the 

 next subject to be taken up is that of the response of the 

 digestive mucosa. And here we have to determine, first, 

 whether or not there is, broadly speaking, any continuity 

 between the responses of digestive organs and those which 

 we have just been studying ; and, secondly, to what extent 

 the functional specialisation of the tissue has acted in 

 accentuating certain of its responsive peculiarities. 



Surveying the function of digestion as a whole, we see 

 that it consists, briefly, of two different processes those, 

 namely, of a previous secretion, by which food is rendered 

 soluble, and of a subsequent absorption, by which the dis- 

 solved foodstuffs are absorbed. In the membrane of the 

 simplest digestive organ, then, the epithelial Alining, using 

 th^t term in its most inclusive sense, must be endowed with 

 the two properties of secretion and absorption under different 



