The alligator and its allies

by A. M. Reese

The Oral Cavity

The mouth in the Crocodilia is large, as is well known, and may be opened very wide. It is bounded anteriorly and laterally by the teeth of the two jaws; these teeth were described in connection with the skull. The mucous membrane of the roof of the mouth and of the dorsum of the tongue, especially the former, exhibits numerous small papillæ (see [page 160]), and among these, in the posterior region of the mouth, are the ducts of mucous glands.

Fig. 33. Interior of the Mouth of A. Mississippiensis

f, transverse fold at the base of the tongue; v, v, velum palatinum.

The tongue extends from just back of the mandibular symphysis to the glottis. It is attached throughout its entire ventral side except for a short distance at its tip, so that it may be elevated and depressed but not protruded. Among the papillæ on its dorsal surface are sense organs, said to be tactile and gustatory corpuscles (see page 165). The posterior margin of the tongue is elevated as a transverse fold that meets a corresponding fold, the velum palatinum, from the lower side of the palate and completely shuts off the mouth from the openings of the trachea and gullet ([Fig. 33]). Into this hinder chamber open the posterior nares, so that the animal can open its mouth under water without getting water into its trachea; or it may, while holding its prey in its mouth, come to the surface to breathe, without danger of letting water into its trachea. The nasal passages, leading from the nostrils to the posterior nares, are, of course, completely inclosed by bone, as described in connection with the skull. Ventral to the larynx and posterior part of the mouth is the large, shield-shaped hyoid apparatus, [Fig. 25], h, also described in connection with the skull.

The Œsophagus

The œsophagus, [Fig. 34], e, is long and of about the same diameter throughout except possibly for a slight enlargement of the anterior region where it leaves the pharynx. The two “olivary enlargements” mentioned by Chaffanjon ([15]) are not always present, and when seen were found to contain either food or small stones or both.

The outside of the œsophagus is smooth and muscular while the lining is thrown into numerous longitudinal folds that in the empty œsophagus nearly obliterate the lumen; where distended by food or pebbles the longitudinal folds may be almost obliterated. In a thirty-inch animal the œsophagus is about six inches long, and opens suddenly, but without any apparent valve, into the large chamber of the stomach. The histology of the œsophagus and the other regions of the digestive tract will be described later.