[Illustration: FIG. 77.--Stomach of _Cercopithecus cephus_, moustache monkey. (Columbia University Museum, No. 158.)] In some forms, as the pig, the left extremity of the stomach carries a caecal appendix with a spiral valve in the interior separating its lumen from the general gastric cavity (Fig. 78). Others have two such caecal appendices added to the left end of the stomach (Peccary, Fig. 79). These caecal pouches may arise from the _body_ of the stomach, instead of from the left extremity. An example of this condition is furnished by the American manatee (Fig. 68). [Illustration: FIG. 78.--Stomach of _Sus scrofa_, pig. The fundus of the stomach carries a caecal appendage separated in the interior by a spiral fold of the mucous membrane from the gastric cavity.] [Illustration: FIG. 79.--Stomach of _Dicotyles torquatus_, peccary. The fundus is a capacious pouch prolonged ventrally and dorsally into two caecal appendages resembling the single appendage of the pig's stomach. (Columbia University Museum, No. 1806.)] =5. Variations in the Form of the Stomach Depending upon the Assumption by the Stomach of Special Functions, which are Usually Relegated to other Organs.=--These functions are the following: (_a_) Storage of food in special receptacles or compartments for subsequent use. (_b_) Mastication of the food is in some animals accomplished only partly or not at all in the mouth, and is then performed in the stomach. A portion of the stomach is thus converted into an apparatus for mastication. (_c_) The provisions for these two accessory functions may be combined in the same stomach. (_a_) Many of the higher vertebrates possess in connection with the alimentary tract additional reservoirs for the storage of food until used. Such reservoirs are found in mammals and birds connected with the oral cavity, as cheek-pouches, or with the oesophagus, such as the crop of the birds (Fig. 88). Fig. 80 shows the development of the cheek-pouches in one of the primates, _Macacus nemestrinus_. [Illustration: FIG. 80.--_Macacus nemestrinus_, pig-tail macaque monkey; cheek-pouches. (From a fresh dissection.)] In many mammals reservoirs of similar import are added directly to the stomach and form an integral part of the organ. Examples are furnished by the compound stomachs of many rodents, ruminants, cetaceans and herbivorous edentates. The peculiar appearance of these stomachs is explained if the additional reservoirs are in imagination removed and the digestive stomach proper restored so to speak to the type-form. The proximal or cardiac portion of the stomach in many rodents is devoid of gastric glands and must be interpreted as a storage chamber for food (Fig. 81). The same significance attaches to the corresponding portion of the manatee's stomach (Fig. 68). [Illustration: FIG. 81.--Stomach of _Cricetus vulgaris_, hamster. (Nuhn.)]