(_b_) The increase of the length of time during which the food remains in the stomach subject to the action of the gastric juice can be accomplished in one of several ways. 1. The stomach, while it retains its general tubular form increases considerably in length and assumes the shape and structure found in the human large intestine. It is partially subdivided by folds projecting into the interior and separating compartments resembling the colic cells of the human large intestine. The time required for the passage of food through the stomach is thus increased and the action of the gastric juice is prolonged and rendered more intense. Such modifications of the structure of the stomach are encountered in _Semnopithecus_ among the monkeys and in the kangaroo, among marsupials (Figs. 70 and 71). [Illustration: FIG. 70.--Stomach of _Halmaturus derbyanus_, rock kangaroo. (Columbia University Museum, No. 582.)] [Illustration: FIG. 71.--Stomach of _Semnopithecus entellus_, entellus monkey. (Columbia University Museum, No. 62/1805.)] 2. The same purpose is accomplished by the development of diverticula from the stomach, in which the food is retained and acted on by the gastric juice for longer periods. The herbivora, omnivora and such carnivora as live on animal food difficult of digestion furnish examples of this type of stomach. The same is also found in most teleosts. In the latter the caecal gastric pouch lies in the long axis of the body, opposite the entrance of the oesophagus. A marked example of this arrangement is seen in the stomach of the eel, _Anguilla anguilla_ (Fig. 72). [Illustration: FIG. 72.--Alimentary canal of _Anguilla anguilla_, eel. (Columbia University Museum, No. 1271.)] In other forms, and in the mammalia especially, the blind pouch is developed from the portion of the stomach lying to the left of the oesophageal entrance at the cardia, and is hence placed transversely to the long axis of the body. This difference in the position of the cul-de-sac is explained by the small transverse measure of the body in teleosts, while the greater amount of available space in the abdominal cavity of mammalia permits of the transverse position of the entire stomach and of the development of the diverticulum from its left extremity. Most mammals have only a single pouch, whose size varies with the digestibility of the food habitually taken. It is greater in herbivora (Figs. 64 and 73) than in omnivora and carnivora (Figs. 74 and 75). In some of the latter, as _Lutra_ (Fig. 63), the cul-de-sac is almost wanting. [Illustration: FIG. 73.--Stomach of _Lepus cuniculus_, rabbit. (Nuhn.)] [Illustration: FIG. 74.--Stomach of _Nasua rufa_, coati. (Nuhn.)] [Illustration: FIG. 75.--Stomach of _Felis leo_, lion. (Nuhn.)] [Illustration: FIG. 76.--Stomach of _Erethizon dorsatus_, American porcupine. (Columbia University Museum, No. 358.)]