CUTANEOUS EXHALATION. 421 



general system, which results from the "wear and tear" of the bodily 

 and mental powers. 



749. The Mucous surface of the Alimentary Canal is furnished, like 

 the skin, with a vast number of glandulae, varying in complexity, from 

 the simple follicle, to a mass consisting of numerous lobules opening 

 into a common excretory duct. The functions of these, as already 

 pointed out, are equally various. The simple follicles appear destined, 

 for the most part, to secrete the protective mucus, which intervenes 

 between the membranous wall and the substances contained in the 

 canal, and which serves to protect the former from the irritating action 

 of the latter. The more complex follicles of the Stomach elaborate 

 the Gastric fluid, which is the prime agent in the digestive process 

 ( 496). The still more elaborate glandulae of Brunner, situated in the 

 walls of the duodenum, also seem to furnish a product which is con- 

 cerned in the digestive operation ( 480). But there is strong reason 

 to believe, that the function of the Peyerian glandulge, which beset the 

 walls of the lower part of the intestinal canal, is purely excretory ; and 

 that they are destined to eliminate putrescent matters from the blood, 

 and to convey them, by the readiest channel, completely out of the 

 body. That the putrescent elements of the faeces are not immediately 

 derived from the food taken in, so much as from the secreting action of 

 the intestinal glandulae, appears from this consideration ; that faecal 

 matter is still discharged, even in considerable quantities, long after 

 the intestinal tube has been completely emptied of its alimentary con- 

 tents. We see this in the course of many diseases, when food is not 

 taken for many days, during which time the bowels are completely 

 emptied of their previous contents by repeated evacuations ; and what- 

 ever then passes, must be derived from the intestinal walls themselves. 

 Sometimes a copious flux of putrescent matter continues to take place 

 spontaneously ; whilst it is often produced by the agency of purgative 

 medicine. The " colliquative diarrhoea," which frequently comes on 

 at the close of exhausting diseases, and which usually precedes death 

 by starvation, appears to depend, not so much upon a disordered state 

 of the intestinal glandulae, as upon the general disintegration of the 

 solids of the body, which calls them into extraordinary activity, for the 

 purpose of separating the decomposing matter. 



750. Thus we perceive, that we have here, also, to watch for the 

 indications of Nature; and that this extensive / system of intestinal 

 glandulae, being the principal channel for the elimination of putrescent 

 matters from the blood, should be especially attended to, when there 

 is reason to think that such matters are present in too large an amount. 

 Hence, when diarrhoea is already existing, we may often" do more good 

 by allowing it to take its course, or even by increasing it by the agency 

 of purgative medicines, than by attempting to check it, and thus 

 causing the retention of the morbid matter in the circulating current. 

 But, on the other hand, it is necessary to bear in mind the extreme 

 irritability of the intestinal mucous membrane ; and carefully to avoid 

 exciting it, when it is already in excess, or when there is danger that 

 it will supervene, as in that form of Fever in which there is a peculiar 



