The Gastric Peristalsis or Motor Func tion of the Stomach.— This is perhaps the most important function of the stomach, for not only does the motor function mix and churn up the gastric contents, but it expels them at the proper time into the bowels. • An animal might live without a gastric secretion, or with a stomach which could not absorb anything, but it could not live with a stomach that had no peristalsis. The musculat layer of the stom ach is much thicker and stronger at the pyloric end, which is near the outlet toward the in testine, than at the cardiac end, which is the dilated rounded pouch extending in the oppo site direction. The cardiac end of the stomach is therefore mostly quiet during the digestive act, and the principal' gastric movements of churning and expulsion occur in the pyloric end where the muscles are strongest. According to Oppel, the cardiac or quiet end of the stom ach in certain animals, like the horse, pig and functionally distinct from the pyloric end. It is lined by a different kind of epthelium called pavement epthelium and its glands have no acid secretion. Accordingly this quiet region is, even under normal conditions, the seat of active starch digestion. It has been that, inasmuch as the starch-converting agency of the saliva could not act in the presence of an acid like that of the gastric secretion, there fore, all starch digestion was arrested in the stomach and was not resumed until the food reached the intestine. That this is not, the case is shown by W. B. Cannon, who proved that in man as in other animals the cardmc end of the stomach serves chiefly for starch diges tion by the action of the salivary ptyalin dur ing the early part of digestion in the stomach. ((American journal of Physiology,' Vol. VI, p. 396). This again emphasizes the importance of thorough mastication, for only thereby can the food be thoroughly penetrated by the saliva and further starch conversion take place in the cardiac end of the stomach during gastric di gestion.
The movements which food undergoes in the stomach during digestion can be studied by the aid of the X-rays. An inert and in soluble substance which is capable of cutting off the X-rays must be mixed with the food in order to make the gastric movements visible before the Roentgen apparatus. Bismuth sub nitrate answers this purpose admirably. Even the movements of the human stomach can be studied by adding this insoluble substance to the food and placing the individual who has eaten it before the X-ray instrument. In this way it has been discovered that the pyloric or highly muscular portion of the stomach is the part where the most effective gastric movements are brought about. The movements in the other portions of the stomach are not of sufficient force to be noticeable before the X-ray appa ratus. It seems probable, therefore, that the fundus or pouch end of the stomach serves simply push the food into the pyloric end, where it is churned to and fro for a while and eventually expelled into the duodenum. Three or four inches from the exit of the stomach, known as the pylorus, the musculature of the stomach is particularly strongly developed (sphincter muscle of the antrum pylori) ; and here it is that the stomach may constrict to such an extent as to partition off a special por tion of the pyloric end and expel the food into the duodenum without permitting of any regurgitation into the fundic end. All this is in contradiction of the view originally held by Beaumont and still quoted in some of the textbooks of physiology, namely, that there is a regular circuit of food around the walls of the gastric cavity.
Structure of the, It is impossible to enter here into a consideration of the micro scopic structure of the stomach, although this is indispensable for the proper understanding of its abnormal functioning. Much is yet to be learned concerning the cells of the peptic glands and their function. It is certain, how ever, that the different products of the gastric secretion, the hydrochloric acid and the fer ments, do not originate in the same cells, but that there are acid-producing cells and fer ment-producing cells in the glands within the stomach. It is even conceivable that the differ
ent ferments of the stomach are produced by different cells. The organ is composed of five different coats. Passing from without inward, these are (1) the peritoneal; (2) the muscular coat, which is in turn composed of the longi tudinal and circular layers; (3) a connective tissue layer; (4) a very small thin layer of muscular tissue, called the muscularis mucos•, separating the connective tissue from the gland ular layer; (5) the glandular layer itself, in nermost of all. In addition to these structures the stomach is permeated by arteries and veins, a liberal network of lymphatics and is richly supplied with nerves. The glandular layer is bordered by a stratum of columna epithelial cells, The Abnormal Digestion of the Stomach; Gastric Diseases.— One of the first and most important things to decide when an individual complains of dyspepsia, or of any distress, pain, distention or symptom referable to the stomach, is whether the signs and symptoms are really traceable to the stomach or not. For one may have all the symptoms of gastric disease and yet the stomach itself may not be abnormal either in structure or function. For instance, the stomach may give rise to abnormal sensations as a consequence of disease of other organs. The organs which most frequently derange the stomach in this manner are the heart, liver and kidneys. Even physicians of experience who have become afflicted with abnormal gastric digestion have been at times deceived ing the true source of their malady. Fully two-thirds of all gastric sufferers who come to special clinics devoted to eases of the stomach are ing not from any primary ease of the stomach whatever, but either from a nervous affection of the stomach or from one of the gastric ments that are secondary to disease of other organs. haps the most frequent of these disorders are those that are due to the nervous gastric affection, or as they are called, the gastric neuroses. To termine precisely the exact nature of an affection of the stomach, the chemical analysis and microscopic examination of known test-meals is able. According to the gravity of the morbid condition, a heavy or a light test-meal is given and a certain time after it is eaten the stomach tube is passed into the stomach and a certain amount of the gastric contents drawn for analysis. As long as this is not done, all deductions from the symptoms and signs alone are conjectural. 'That is not to say that the inferences drawn from test-meal analysis and microscopical examination of test-meals are always conclusive. It is quently necessary to examine also the blood and the urine of the patient and even to amine the stools after certain test-meals. Recently the method of fractional analysis of test-meal samples drawn at short intervals has been rediscovered. In a way it is of interest to ascertain the time relations of the gastric secretion, that is, when it reaches its height. Clinically, however, the expediency, feasibility and possibility of this method are still dice.D Then all the other organs of the body should be carefully examined, bearing in mind that it is not always correct to presume that a patient has a disease of his stomach because he has gastric symptoms. The reverse is equally true, that a patient may have no symptoms ever referring to the stomach and yet have very grave disease of this organ. The gravest tion which may befall the organ — cancer of the stomach-- has been known to run its entire course and cause death in a latent manner; that is, without giving a single symptom re ferrable to the stomach. This is an instance where a patient may have a gastric disease and no gastric symptom. A person who suffered from almost complete blindness, yet manifested no disease in his eyes, was found after exhaus tive study to have been thus affected by a poison circulating in his blood, which was ab sorbed from his gastrointestinal canal and was due to an abnormal digestion. Under treat ment directed toward his stomach and intestine his vision gradually returned.