10 THE STRUCTURE AND FUNCTIONS 



vesicles ceases, the lacteals empty themselves, and the villi be- 

 come flaccid. 



The function of the villi now ceases till they are again roused 

 into action by another flow of chyme along the gut. 



During the intervals of absorption, it becomes necessary to 

 protect the delicate villi from the matters contained in the bowel. 

 They had thrown off their protective epithelium when required 

 to perform their functions, just as the stomach had done to afford 

 gastric juice, and the intestinal follicles to supply their peculiar 

 secretions. In the intervals of digestion, the epithelium is 

 rapidly reproduced. 



The germinal membrane, which, as I have stated, not only 

 forms the outer membrane of the follicles, under the epithelia, 

 but also the under-lying membrane of the villi, contains in its 

 substance germinal centres of an oval form, situated at pretty 

 regular distances. From these the epithelium appears to be 

 reproduced during the intervals of absorption, as stated in the 

 first chapter. 



During this process of developement, the primary membrane 

 appears to split into two laminae, the epithelia passing out from 

 its nuclei between these. This would account for the epithelia, 

 particularly the prismatic and conical, adhering by their free 

 extremities. 



Such are the processes which would appear to take place in 

 the villi of the intestinal tube during digestion and absorption. 

 When considered in relation to the functions of digestion and 

 absorption of chyle, these processes are highly interesting. 



The labours of the chemist have now so far simplified the 

 theory of digestion, as to deprive the stomach of their vitalizing 

 or organizing powers so long ascribed to it. 



Every step in this chemico-physiological inquiry leads to the 

 conclusion, that the changes which the food undergoes while in 

 the cavity of the gut are entirely of a chemical nature. 



If we continue, then, to apply the term digestion to that series 

 of processes by which the aliment is assimilated to the matter of 

 which the body is composed, we must divide the series into two 

 groups. The first group will include all those changes which 



