DIGESTION. 



CHAP TEE VIII. 



STOMA CH-DIGESTION. 



Physiological anatomy of the stomach Peritoneal coat Muscular coat Mucous coat Glandular apparatus in the 

 stomach Gastric, or peptic glands Mucous glands Closed follicles Gastric juice Mode of obtaining the gas- 

 tric juice Gastric fistula in the human subject in the case of St. Martin Secretion of the gastric juice Composi- 

 tion of the gastric juice Source of the acidity of the gastric juice Ordinary saline constituents of the gastric juice 

 Action of the gastric juice in digestion Constituents upon which the activity of the gastric juice depends Ac- 

 tion of the gastric juice upon meats Action upon albumen, fibrin, caseine, and gelatine Action upon vegetable 

 nitrogenized principles Albuminose, or peptones Action of the gastric juice upon fats Action upon saccharine 

 and amylaceous principles Duration of stomach-digestion Digestibility of different aliments in the stomach 

 Circumstances which influence stomach-digestion Character of the contractions of the muscular coat of the 

 stomach Movements in the cardiac and in the pyloric portion Mechanism of the movements of the stomach 

 Eumination, and rcgurgitation from the stomach Summation in the human subject Eructation. 



Physiological Anatomy of the Stomach. 



THE most dilated portion of the alimentary canal, in man, is the stomach. It serves 

 the double purpose of a receptacle for the food and an organ in which certain important 

 digestive processes take place. It is situated in the upper part of the abdominal cavity 

 and is held in place by folds of the peritoneum and by the oesophagus. Its form is not 

 easily described. It has been compared to a bagpipe, which it resembles somewhat, 

 when moderately distended. As we should naturally suppose from the fact that the 

 stomach periodically receives considerable quantities of solids and liquids, its form and 

 position are subject to great variations. "When empty, it is flattened, and in many parts 

 its opposite walls are in contact. When moderately distended, its length is from thirteen 

 to fifteen inches, its widest diameter, about five inches, and its capacity, one hundred and 

 seventy-five cubic inches, or about five pints. The parts usually noted in anatomical de- 

 scriptions are : a greater and a lesser curvature ; a greater and a lesser pouch ; a cardiac, 

 or oasophageal opening ; and a pyloric opening, which leads to the intestinal canal. The 

 great pouch is sometimes called the fundus. 



The coats of the stomach are three in number; the peritoneal, muscular, and mucous. 

 By some, the fibrous tissue which unites the mucous to the muscular coat is regarded as 

 a distinct covering and is called the fibrous coat. 



Peritoneal Coat. This is simply a process of the peritoneum, similar in structure to 

 the membrane which covers the other abdominal viscera. It is a reflection of the mem- 

 brane which lines the general abdominal cavity, which, on the viscera, is somewhat thin- 

 ner than it is on the walls of the cavity. Over the stomach, the peritoneum is from -$-3 

 to Fro f an i ncn m thickness. It belongs to the class of serous membranes and con- 

 sists of fibres of the white inelastic tissue, mingled with a considerable number of elastic 

 fibres. It is closely adherent to the subjacent muscular coat and is not very abundantly 

 supplied with blood-vessels and nerves. Lymphatics have been demonstrated only in the 

 subserous structure. The surface of the peritoneum is everywhere covered with regu- 

 larly-polygonal, flattened cells of pavement or tessellated epithelium, closely adherent to 

 each other and presenting a perfectly smooth surface which is continually moistened 

 with a small quantity of watery secretion. An important function of this membrane is 

 to present a smooth surface covering the abdominal parietes and viscera, so as to allow 

 of free movements of the organs over each other and against the walls of the abdomen. 



Muscular Coat. Throughout the whole of the alimentary canal, from the cardiac 

 opening of the stomach to the anus, the muscular fibres forming the middle coat are of 



