. Essentials of biology presented in problems. Biology. 328 MAN, A MAMMAL. The skull: F., frontal bone; P., parietal bone ; T., temporal bone ; SP., sphenoid bone; O., occi- pital bone; , superior maxillary (upper jaw) bone ; , inferior maxillary (lower jaw) bone. The Human Skull. — The skull stows wonderful adaptations for its varied functions. The brain case is compactly built, its arched roof giving strength. The eye and inner ear are protected in sockets of bone. The lower jaw works upon a hinge, and furnishes attach- ment for strong muscles which move the jaw. The skeleton, beside
. Essentials of biology presented in problems. Biology. 328 MAN, A MAMMAL. The skull: F., frontal bone; P., parietal bone ; T., temporal bone ; SP., sphenoid bone; O., occi- pital bone; , superior maxillary (upper jaw) bone ; , inferior maxillary (lower jaw) bone. The Human Skull. — The skull stows wonderful adaptations for its varied functions. The brain case is compactly built, its arched roof giving strength. The eye and inner ear are protected in sockets of bone. The lower jaw works upon a hinge, and furnishes attach- ment for strong muscles which move the jaw. The skeleton, besides the purposes already described, protects certain organs in the body cavity of man. Other Organs. ^—We have seen that a body cavity has developed in aU animals which are more complex than the baglike hydra, and that a food tube has come to lie within this space. In all such animals the structures which have to do with digestion and absorption of food, most of the structures which have to do with the circulation of this food and of the blood, and organs which give oxygen to the blood, as well as the organs of excretion and of reproduction, he within the body cavity. These organs we shall discuss in detail later. Nerves. — Other structures, known as nerves, are found in prac- tically all parts of the body. We find that nerves have their end- ings in the skin, in muscle, and in the cells of glands in various parts of the body; we find a nerve supply to the heart, lungs, and other structures within the body cavity. The most important part of the nervous system in vertebrate animals lies within the cavity formed by bones making up the skull and the vertebral column. This central nervous system, the spinal column and the bram, is a characteristic of the vertebrate animals. General Functions of the Nervous System. — We have seen that, in the simplest of animals, one cell performs the functions neces- sary to its existence. In the more complex animals, where groups of cells fo
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
