Ptyaline is the salient feature of saliva. It is known as a ferment--acting upon starch and converting it into dextrine and grape sugar. The action of saliva varies in intensity in different animals. The food after having been acted upon and prepared is propelled, by the act of deglutition, through the æsophagus into the stomach, by way of the pharynx. The pharynx is that part of the alimentary canal which unites the cavities of the mouth and nose to the æsophagus. It extends from the base of the skull to the lower border of the cricoid cartilage, and forms a sac open at the lower end, and imperfect in front, where it presents apertures leading into the nose, mouth, and larynx. The pharynx is about four and a half inches in length, and is considerably wider across than it is deep from before backwards. The æsophagus or gullet, the passage leading from the pharynx into the stomach, commences at the cricoid cartilage opposite the lower border of the fifth cervical vertebra, descends in front of the spine, passes through the diaphragm opposite the ninth dorsal vertebra, and ends by an opening at the cardiac orifice of the stomach. It is from nine to ten inches in length. The stomach is situated in the abdominal cavity. It lies in part against the anterior wall of the abdomen, and in part beneath the liver and diaphragm, and above the transverse colon. It is somewhat conical or pyriform in shape. The left part is the larger, and is named the cardiac, or splenic, the right is named the pyloric, extremity. The upper border is about three or four inches in length, is concave, and is named the lesser curvature, while the lower border is much longer, is convex, and forms the greater curvature. The dimensions vary greatly in different subjects, and also according to the state of distension of the organ. When moderately filled, its length is about ten to twelve inches, and its diameter at its widest part from four to five inches. It weighs when freed from other parts about four and a half ounces in the male and somewhat less in the female. The structure of the stomach consists of four coats--a serous, a muscular, an areolar, and a mucous coat. The external or serous coat is derived from the peritoneum. There are three kinds of muscular fibers--longitudinal, circular, and oblique, and the internal mucous lining is a rather thicker, soft, smooth, pulpy membrane, lying in ridges or rugæ, and containing a large number of glands--tubular or gastric glands, and another variety of gland called peptic, besides others.