The alimentary canal is a tube which extends from the mouth to the anus. It has a complete lining of mucous membrane, external to which is an almost continuous muscular coat. The abdominal portion of the tube is largely covered with a serous membrane, the visceral peritoneum. The canal consists of the following consecutive segments: mouth, pharynx, first portion of the esophagus, crop, second portion of the esophagus, proventriculus, gizzard, small intestine, large intestine, and cloaca. The accessory organs are beak, tongue, salivary glands, liver, and pancreas. =The Mouth= (Fig. 27).—The distinctive character of the mouth of the fowl consists, in the absence of lips and teeth and instead of jaw bones of other animals, of a _beak_. The edge of the beak is covered by a horn-like gum. The shape of the beak differs in the various classes of birds. In the chicken the beak is short, strong, thick, and pointed; in palmipeds it is flattened. The upper mandible extends out over the lower mandible. The outer portion of the upper and the lower beaks is covered by a horny sheath. There is no velum, and the mouth cavity is extended rather continuously into the pharynx (Fig. 27, No. 4). The posterior cross bar of the hard palate (Fig. 27, No. 5), which possesses a row of filiform papillæ projecting backward, marks the upper boundary line of the mouth; while the posterior end of the tongue (Fig. 27, No. 6), likewise with a row of filiform papillæ, marks its lower boundary line. _Parts of the Mouth._—The mouth of fowls is divided into an upper and a lower half. The upper half is divided into an anterior and a posterior part. The anterior part extends from the anterior tip of the beak to the posterior nares. It is further divided into an outer hard part and an inner soft part. The outer part is covered by epithelium which may be considered as a continuation from the upper outer portion of the beak. A portion of this is cornified. The inner part is covered by a mucous membrane containing mucous glands, nerves, and blood-vessels. In the posterior part of the upper half of the mouth, are situated the posterior nares (Fig. 27, No. 10) which appear as a longitudinal slit in the center of the hard palate. There is also found in this part a furrow which contains the opening of the Eustachian tubes, or tubæ auditivæ. There are also two ridges near the same posterior part in which are red and white papillæ, which may appear in rows, and which contain mucous glands. [Illustration: FIG. 27.—Mouth and pharynx of a cock laid open. 1, Eye. 2, Edge of beak covered with a horn-like gum. 3, Tongue. 4, Pharynx. 5, Posterior cross bar of hard palate. 6, Posterior end of tongue. 7, Anterior end of esophagus. 8, Phrenum. 9, Palatal papillaries. 10, Posterior nares. ]