. A text-book in general physiology and anatomy. Physiology, Comparative; Anatomy. BEPTILE SKELETONS 259 is the necessity for a stiff framework against which the legs may push in propelling the body. If the backbone were too flexible it would simply bend when the legs pushed against it, and the animal would not move any more than does an object when pushed with a feather. The frog skeleton will be seen to differ from that of the higher forms of animals, though not so much as from that of the fish. For example, the frog has a much shorter back- bone than is found in higher forms, the ribs are w
. A text-book in general physiology and anatomy. Physiology, Comparative; Anatomy. BEPTILE SKELETONS 259 is the necessity for a stiff framework against which the legs may push in propelling the body. If the backbone were too flexible it would simply bend when the legs pushed against it, and the animal would not move any more than does an object when pushed with a feather. The frog skeleton will be seen to differ from that of the higher forms of animals, though not so much as from that of the fish. For example, the frog has a much shorter back- bone than is found in higher forms, the ribs are wanting, and the skull is made up largely of face bones with a very tiny cranium or brain box. As a machine for support and motion, it is very primitive compared with our skeleton. The legs are so attached that the thigh bones point out- ward from the body instead of being under the part to be supported. The shoulder girdle is rigid and the elbows point outward, which makes it awkward to use the front legs as pushing agents. In fact, in the frog these front legs are of smaU use in locomotion on land; the greatly elongated hind legs being so arranged as to make leaping the natural mode of progress. Reptile skeletons.— The reptiles differ from the amphibi- ans in possessing ribs (see Fig. 109), which have been de-. FiG. 109 — Skeleton of a crocodile. veloped to protect the sides of the body and to aid in the operation of the lungs as breathing organs. In the snakes the legs are lacking and there is no breastbone. In all the. 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 Eddy, Walter Hollis, b. 1877. New York, Cincinnati [etc. ] American book Co
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