270 OF POOD AND THE DIGESTIVE PROCESS. 



from the stomach, and undergo no subsequent alteration in the intes- 

 tinal canal ; so that they are discharged among the faeces as completely 

 useless. 



474. We have now to notice the conditions, under which the Gas- 

 tric fluid is secreted ; the knowledge of which is of great practical im- 

 portance. We have seen that it is not poured forth, except when food 

 is introduced into the stomach, or when its walls are irritated in some 

 other mode ; and there is reason to believe, that it is not previously 

 secreted and stored up in the follicles, but that the act of secretion 

 itself is due to the stimulus applied to the mucous membrane. The 

 quantity of the fluid then poured into the stomach, however, is not 

 regulated by the amount of food ingested, so much as by the wants of 

 the system ; and as only a definite quantity of food can be acted on by 

 a given amount of gastric juice, any superfluity remains undissolved for 

 some time, either continuing in the stomach until a fresh supply of the 

 solvent is secreted, or passing into the intestinal canal in a crude state, 

 and becoming a source of irritation, pain, and- disease. The use of a 

 small quantity of salt, pepper, mustard, or other stimulating substances, 

 appears to produce a gently stimulating effect upon the mucous mem- 

 brane, and by causing an increased afflux of blood, to augment the 

 quantity of the gastric fluid poured forth. Any excess of these or other 

 irritants, however, produces a disordered condition of the mucous mem- 

 brane, which is very unfavourable to the digestive process. It becomes 

 red and dry, with an insufficient secretion of mucus ; the epithelial 

 lining is abraded, so that the mucous coat is left entirely bare ; and 

 irregular circumscribed patches of a deeper hue, sometimes with small 

 aphthous crusts, present themselves here and there on the walls of the 

 stomach. Similar results follow excess in eating. When these changes 

 are inconsiderable, the appetite is not much impaired, the tongue does 

 not indicate disorder, and the digestive process may be performed ; but 

 if they proceed further, dryness of the mouth, thirst, accelerated pulse, 

 foulness of the tongue, and other symptoms of febrile irritation, mani- 

 fest themselves ; and no gastric secretion can then be excited by the 

 stimulus of food. Similar results may follow the excitement of the 

 emotions ; and those of a depressing nature seem especially to produce 

 a pale flaccid condition of the mucous membrane, which is equally 

 unfavourable to the due secretion of gastric, fluid. 



475. That the amount of the secretion is ordinarily proportioned to 

 the wants of the system, that the introduction of any superfluous 

 aliment into the stomach is not only useless but injurious, as giving rise 

 to irritation, that incipient disorder of the stomach may occur, render- 

 ing it less fit than usual for the discharge of its important duties, without 

 manifesting itself by the condition of the tongue, that when the tongue 

 does indicate disorder of the stomach, such disorder is usually consider- 

 able, and that every particle of food ingested, in such states as prevent 

 the secretion of gastric fluid, is a source of fresh irritation, are truths 

 which cannot be too constantly kept in mind. There can be no doubt 

 that the habit of taking more food than the system requires, is a very 

 prevalent one ; and that it is persevered in, because no evil result svems 

 to follow. But when it is borne in mind that this habit must keep the 



