. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. REPTILES 289 Locomotion. — Locomotion is performed by pulling and push- ing the body along the ground, a leverage being obtained by means of the broad flat scales, or scutes, with which the ventral side of the body is covered. Snakes can also move without twist- ing the body. This is accomplished by a regular drawing forward of the scutes (with the ribs under them) and then pushing them backward rather more violently. Feeding Habits. — The bones of the jaw are very loosely joined together.
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. REPTILES 289 Locomotion. — Locomotion is performed by pulling and push- ing the body along the ground, a leverage being obtained by means of the broad flat scales, or scutes, with which the ventral side of the body is covered. Snakes can also move without twist- ing the body. This is accomplished by a regular drawing forward of the scutes (with the ribs under them) and then pushing them backward rather more violently. Feeding Habits. — The bones of the jaw are very loosely joined together. Thus the mouth of the snake is capable of wide disten- tion. It holds its prey by means of incurved teeth, two of which (in the poisonous snakes) are hollow, and serve as a duct for the passage of poison. The poison glands are found at the base of the curved' fangs in the upper jaw. The tongue is very long and cleft at the end. It is an organ of touch and taste, and is not, as many people believe, used to sting with. The food is swallowed whole, after having been caught by the teeth, and pushed down by rhythmic contractions of the muscles surrounding the gullet. They refuse other than living prey. After a full meal, one of which is sufficient for weeks, the snake remains in a torpid condition. Adaptations. — The extreme length of the body in the snake has resulted in the modification of the form of its internal organs. One long, narrow lung is developed instead of two. The glands of the body cavity are long and slender, while the kidneys are placed so that one is anterior to the other. Snakes are usually colored to harmonize with their surround- ings. Thus they may approach and seize their prey before it escapes. They are not extremely prolific animals, but hold their own with other forms of life, because of their numerous adaptations hunter's BIOL. — 19. Skull of boa constrictor, two thirds natural size. From photograph by Please note that these images are ex
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