FIG. 35.—A median antero-posterior section through the body of a 1-pound pullet. 1, First portion of the esophagus. 2, Crop. 3, Second portion of the intestine. 4, Proventriculus. 5, Gizzard. 6, Spleen. 7, Liver. 8, Heart. 9, Point where duodenum was severed from gizzard. 10, Point where duodenum was severed. 11, Duodenum. 12, Pancreas. 13, Cæcum. 14, Floating small intestine. 15, Ovary. 16, Oil sac. ] =The Small Intestine= (Fig. 31, No. 8 and 9).—The small intestine, intestinum tenue, is the tube which connects the gizzard with the large intestine. It is divided into two parts, the duodenum and the free portion. Of the three parts as considered in the mammalian intestine, only the first, the _duodenum_, can be distinguished. There is no demarcation between the jejunum and the ileum. The jejunum and the ileum or that part which represents these sections, are in coils suspended from the free border of the mesentery the other border of which is, in turn, attached to the dorsal wall (Fig. 64). The length of the small intestine in a hen of average size is about 61.7 inches. [Illustration: FIG. 36. _A._ Section of the duodenum of the fowl. 1, Villus. 2, Gland. 3, Mass of lymphoid tissue. 4, Muscularis mucosa. 5, Longitudinal layer. 6, Circular muscular layer. 7, Serous layer. _B._ A section from A at _a_. 1, The striated free border of the cells. 2, Goblet cell. 3, Columnar cell. 4, Nucleus of cell. ] The wall of the small intestine is provided with four coats, as follows: a mucous, submucous, muscular coat made up of two layers—the outer, longitudinal and the inner circular layer, and an external serous. [Illustration: FIG. 37.—Histological studies of various anatomical parts. _A._ A transverse section of the first portion of the esophagus of a fowl. 1, The outer longitudinal muscular layer. 2, The circular muscular layer. 3, The submucosa. 4, The muscularis mucosa. 5, Stroma. 6, Epithelial layer. 7, The lenticular glands. 8, The lumen. _B._ A transverse section of the proventriculus. 1, The outer longitudinal muscular layer. 2, The middle muscular layer. 3, The inner longitudinal muscular layer. 4, Stroma. 5, The muscularis mucosa. 6, The submucosa. 7, Stroma. 8, Tubular glands. 9, Tubulo-alveolar glands. 10, A tubulo-alveolar gland with the tubular glands cut transversely, 11, The lumen of the proventriculus. _C._ A section of the inner wall of the gizzard. 1, The hyaline mucous membrane. 2, Branched tubular glands. 3, Submucosa. 4, Muscle. 5, A connective tissue septum. _D._ A transverse section of the small intestines. 1, The outer longitudinal muscular layer. 2, The inner circular muscular layer. 3, The muscularis mucosa. 4, The stroma. 5, Brunner’s glands. 6, A villus. 7, Mass of lymphoid tissue.