. The biology of the amphibia. Amphibians. THE DIGESTIVE SYSTEM 203 midline and is curved with the convex side toward the left, held in place by two folds of the peritoneum (Fig. 77). Its lining or mucosa consists of a simple, colum- nar epithelium on which there empty great numbers of small glands. Those at the oesophageal end of the stomach consist of a long neck of the same structure as the surface epithelium, a few large and trans- parent mucous cells, and one or more diverticula of cells having a granular cyptoplasm (Fig. 78). The latter cells apparently secrete both pepsin- producing gra
. The biology of the amphibia. Amphibians. THE DIGESTIVE SYSTEM 203 midline and is curved with the convex side toward the left, held in place by two folds of the peritoneum (Fig. 77). Its lining or mucosa consists of a simple, colum- nar epithelium on which there empty great numbers of small glands. Those at the oesophageal end of the stomach consist of a long neck of the same structure as the surface epithelium, a few large and trans- parent mucous cells, and one or more diverticula of cells having a granular cyptoplasm (Fig. 78). The latter cells apparently secrete both pepsin- producing granules and hydro- chloric acid. In mammals two different types of cells perform these functions. The glands near the pylorus are comparable to the necks of the other glands. Large mucous cells are occasion- ally found at the bottom of the pyloric glands giving further evidence of this homology. The stomach of Amphibia serves to alter both physically and chemically the food swallowed; it functions also as a place of food storage. Food may be available only at irregular intervals and many frogs are able to expand their stomachs enormously when filling them on these occasions. Intestines.—The intestine in Amphibia is a tube of It is. Fig. 77.—Viscera of Necturus maculosus. , cloacal glands; , dorsal mesentery; H., heart; Int., intestine; K., nearly kidney; Li., liver; Lu., lung; uniform width except posteriorly ^S^f^—, where it widens to form the large T., testis; , urinary biad- • i j • t, . 1 , . l , der; , Wolffian duct. intestine. It is nearly straight (Modified from Cope.) in some caecilians and only slightly folded in Siren and Proteus. Increase in length reaches its extreme stage in the common Rana tadpoles, where the small. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Noble,
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Keywords: ., bookcentury1900, bookpublishernewyorkmcgr, booksubjectamphibians
