With every meal several things are eaten which are not digestible at all. Among them is elastic tissue, forming a part of the connective tissue of all animal foods, and cellulose, which is the chief constituent of the cases which envelope the cells of plants. The mucus secreted by the membrane lining the alimentary tract also contains an indigestible substance, mucin. These three materials, together with some water, some undigested foodstuffs, and some excretory substances found in the various secretions poured into the alimentary canal, form a residue which collects in the lower end of the large intestine, and is from time to time expelled from the body.

Dyspepsia is the common name of a variety of diseased conditions attended with loss of appetite or troublesome digestion. Being often unattended with acute pain, and if it kills at all doing so very slowly, it is pre-eminently suited for treatment by domestic quackery. In reality, however, the immediate cause of the symptoms, and the treatment called for, may vary widely; and the detection of the cause and the choice of the proper remedial agents often call for more than ordinary medical skill. A few of the more common forms of dyspepsia may be mentioned here, with their proximate causes, not in order to enable people to undertake the rash experiment of dosing themselves, but to show how wide a chance there is for any unskilled treatment to miss its end and do more harm than good.

Name some indigestible substances eaten in every ordinary meal. Point out the source of each. What indigestible substance is added in the alimentary canal? What substances are found in the lower end of the large intestine?

What is meant by dyspepsia? Why is it not a wise thing for people to try to treat it themselves without skilled advice?

Appetite is primarily due to a condition of the mucous membrane of the stomach, which in health comes on after a short fast and stimulates its sensory nerves ; and loss of appetite may be due to any of several causes. The stomach may be apathetic and lack its normal sensibility so that the empty condition does not act, as it normally does, as a sufficient excitant. When food is taken it is a further stimulus and may be enough; in such cases "appetite comes with eating." A little quinine or tincture of gentian before a meal is often useful to patients of this class. On the other hand, the stomach may be too sensitive, and a voracious appetite be felt before a meal, which is replaced by nausea, or even vomiting, as soon as a few mouthfuls have been swallowed; the extra stimulus of the food then over-stimulates the too irritable stomach, just as a draught of mustard and warm water will a healthy one. The proper treatment in such cases is a soothing one.* In states of general debility, when the stomach is too feeble to secrete under any stimulation, the administration of weak acids and artificially prepared pepsin is needed, so as to supply gastric juice from outside until the improved digestion strengthens the stomach up to the point of being able to do its own work.

Describe the symptoms of some chief forms of dyspepsia.

* When food is taken it ought to stimulate the sensory gastric nerves, so as to excite the reflex centres for the secretory nerves and for the dilatation of the blood-vessels of the organ; if it does not, the gastric juice will be imperfectly secreted. In such cases one may stimulate the secretory nerves by weak alkalies (p. 174), as apollinaris water or a little carbonate of soda, before meals; or give drugs, as strychnine, which increase the irritability of reflex nerve-centres. The vascular dilatation may be helped by warm drinks, and this is probably the rationale of the glass of hot water after eating which has recently been in vogue: the usual cup of hot coffee after dinner is a more agreeable form of the same aid to digestion.

Enough has probably been said to show that dyspepsia is not a disease, but a symptom accompanying many diseased conditions, requiring special knowledge for their treatment. From its nature—depriving the body of its proper nourishment—it tends to intensify itself, and so should never be neglected; a stitch in time saves nine.