. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 'FISH W ' jAMPHIBIANKT BIRD ^m/ MAMMAL! Fig. 220. Silhouettes of the digestive system. (After Roule.) The ingressive zone is the intake region of prehension and mastication. It involves the lips and mouth with the teeth, tongue, and various other structures contained therein. The progressive zone, embracing the pharynx, esophagus, and stomach, is the region of forwarding the food-intake and passing it through the preliminary stages of modification. The deg
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. 'FISH W ' jAMPHIBIANKT BIRD ^m/ MAMMAL! Fig. 220. Silhouettes of the digestive system. (After Roule.) The ingressive zone is the intake region of prehension and mastication. It involves the lips and mouth with the teeth, tongue, and various other structures contained therein. The progressive zone, embracing the pharynx, esophagus, and stomach, is the region of forwarding the food-intake and passing it through the preliminary stages of modification. The degressive zone, coincident with the small intestine, is not only, the most extensive but also in a sense the most important part of all the zones, for here occurs the chemical preparation of the food stuffs, and their ultimate selection and absorption into the blood. Finally, the egressive zone, which is confined to the large intestine, is the region for the expulsion of the unusable residue that cannot be diverted into the blood and applied to the uses of the body. These regions are shown diagrammatically in silhouette for fishes, am- phibians, birds and mammals, in Figure 220. With this introduction we may now proceed upon an imaginary tour of inspection through the entire alimentary tract, with our eyes open for the anatomical scenery along the way. III. INGRESSIVE ZONE 1. Food Capture and Prehension Before food can travel along the digestive highway, it must be captured and placed inside the entrance of the tube. This process, which may call for expert performance, occupies a large part of the waking hours of most. 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 Walter, Herbert Eugene, b. 1867; Sayles, Leonard Perkins, 1902-. New York : Macmillan Co.
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