Page:The American Cyclopædia (1879) Volume XV.djvu/408

 396 STOMACH toneal coat is a thin serous layer covering the outside of the organ, continuous with the general peritoneal layer of the abdomen. Its moist and smooth external surface enables the stomach and other neighboring organs to glide readily over each other without friction or injury. 2. The muscular coat, immediately beneath the peritoneal covering, is composed of a double series of circular and longitudinal muscular fibres, of the smooth or unstriped variety, whose involuntary alternating con- tractions and relaxations cause the peristaltic movements of the walls of the stomach, and provide for the requisite mixture, transporta- tion, and final expulsion of its contents. 3. The submucous cellular coat is a layer of loose areolar tissue, between the muscular coat and the mucous membrane. The office of this layer is to form such a connection between the muscular and mucous tunics as to keep them in a certain degree of apposition, and yet allow of the folding up of the mucous membrane when the organ is empty, and its expansion when filled with food. 4. The mucous mem- brane of the stomach, its most important tunic in a physiological point of view, is the mem- brane which secretes the gastric juice. Its in- ternal surface is soft and velvety, owing to its being covered with minute conical folds or ridges which are partly distinct and partly con- nected with each other. Its thickness is com- posed of a great number of tubular glands or follicles, the " gastric tubules," which begin at the inferior portion of the mucous membrane by blind extremities, run perpendicularly through its substance, and open by minute orifices upon its free surface into the general cavity of the stomach. These tubules vary somewhat in dif- ferent parts of the stomach. In the pyloric or right-hand portion they are nearly straight and simple in structure, and of the same diameter throughout. In the cardiac or left-hand portion they are more compound, several of them uni- ting, at a little distance below the surface, into comparatively wide circular tubes, lined with cylindrical instead of glandular epithelium. In the middle region of the stomach the gastric glands are also compound ; and their inferior or tubular portions, which are here very long, are filled, in addition to the ordinary glandular epithelium, with very large, rounded, granu- lar, nucleated cells, which often seem to fill nearly their entire cavity, and to project from their sides in such a way as to give them an irregularly tumefied or varicose appearance. The mucous membrane of the stomach is ex- ceedingly vascular, the capillary blood vessels penetrating everywhere between the adjacent tubules, and forming an abundant superficial plexus about their orifices. At the time of di- gestion the quantity of blood circulating in the mucous membrane is greatly increased by an expansion of the smaller arteries supplying the capillary network. The mucous membrane becomes turgid and reddened, the gastric tu- bules enter into a state of functional activity STOMACH (DISEASES OF THE) and begin to pour out the gastric juice, which is to act upon the food. Soon afterward the muscular coat of the organ is in its turn ex- cited to peristaltic action, by which the food is Compound Gastric Tubule, from the middle region of the Stomach, a. Upper or wide portion, lined with cylindri- cal epithelium, o. Lower or tubular portion, lined with glandular epithelium. moved alternately to and fro, from the cardiac toward the pyloric extremity of the organ, and subjected also to a kind of gentle and continu- ous churning process by which the gastric juice exuded from the mucous membrane is made to penetrate every part of the alimentary mass, and come in contact simultaneously with the whole. As digestion proceeds, successive por- tions of the liquefied food are carried through the pylorus into the small intestine ; and as the stomach is thus gradually emptied it resumes its previous condition of repose. The peri- staltic motion comes to an end, the vascular congestion subsides, and the further secretion of gastric juice is suspended until the next period of digestion arrives. STOMACH, Diseases of the. Diseases of the stomach may be classed as inflammatory, structural, and functional. Gastritis or in- flammation of the stomach may be acute, sub- acute, or chronic. It is always attended by certain symptoms, but they are also mostly the symptoms of other diseases. Vomiting is frequent and persistent, but is of itself not sufficient evidence, nor when associated with pain in the epigastric region. The following combination of symptoms may be considered as diagnostic : intense pain of a burning char- acter over the epigastrium, together with shoot- ing pains in the chest, unaccompanied by the physical signs of pulmonary disease, nausea, and