=The Proventriculus.= _Location._—The proventriculus lies in the superior part of the groove formed by the two lobes of the liver, is inferior to the aorta, and is directed slightly to the left, communicating anteriorly with the second portion of the esophagus and posteriorly emptying into the pars muscularis, the gizzard. _Shape._—The proventriculus is round transversely and elongated, in fact, nearly fusiform. In the hen of average size it measures about 1.62 inches long and 0.8 inch in diameter. _Structure._—The wall of the proventriculus has four coats, the mucous, submucous, muscular, and serous. The inner mucous coat which is raised in folds, is lined with columnar epithelial cells. The mucous membrane contains lymphoid tissue. The mucous coat throughout contains simple tubular glands which secrete a highly acid fluid which finds its way to the surface through small cylindrical ducts lying at right angles to the inner surface of the mucous membrane (Fig. 32, No. _B_, 1). [Illustration: FIG. 32.—Gizzard and stomach of the fowl. _A._ 1, Alveolar glands. 2, Mucous membrane of the inner surface of the proventriculus showing the tubular glands. 3, Connective tissue between the alveolar glands. 4, An artery. 5, Muscularis mucosa. _B._ Photograph of the proventriculus and gizzard. 1, Proventriculus showing stomata of glands. 2, End of duodenum. 3, Gizzard showing hornified epithelium formed into grooves. 4, The heavy muscular walls. ] The submucosa, connects the mucous and muscular coats and the muscularis layer throws the mucous membrane into folds. Outside the muscularis mucosa there is another layer (Fig. 32, _A_), of simple tubular glands, grouped in lobules, and lined by cuboidal cells and separated from each other by clefts. These tubular glands converge toward the center and open into the same cavity. The middle muscular coat can be divided into three layers: two thin, longitudinal layers, and a thick, circular layer interposed between the other two. _Function._—The function of the proventriculus appears to be to soak the food with a secretion. The secretion from the proventriculus is similar to that produced by the fundus glands of the stomach of mammals. It contains acid and a ferment-pepsin. =The Gizzard= (Fig. 31, No. 18). _Location._—The gizzard, or muscular stomach, occupies a portion of the central part of the abdominal cavity (Fig. 33, No. 4). It lies slightly to the left and just behind the liver, the proventriculus, and the spleen, and rests upon a mass of intestines. The gizzard communicates at its anterior portion with the proventriculus and with the duodenum. These openings are close together. The gizzards of a large number of hens of average size averaged in weight as follows: full, 0.215 pound; empty, 0.126 pound. The gizzard stands perpendicularly and somewhat obliquely in the abdominal cavity. _Shape._—In shape the gizzard is roundish, flattened laterally.