. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. THE SKELETON 373 the spinal cord. The surface of the centrum and those parts of the vertebrae each of which fits into its next neighbor are covered with pads of cartilage. Two of the processes in each vertebra project forward and two backward; these form articulations or joints with the neighboring vertebrsB. Of the other processes, one projects dorsally and two project laterally; these give attach- ment to the muscles of the back. The two vertebrae directly be- neath the head are modified
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. THE SKELETON 373 the spinal cord. The surface of the centrum and those parts of the vertebrae each of which fits into its next neighbor are covered with pads of cartilage. Two of the processes in each vertebra project forward and two backward; these form articulations or joints with the neighboring vertebrsB. Of the other processes, one projects dorsally and two project laterally; these give attach- ment to the muscles of the back. The two vertebrae directly be- neath the head are modified so as to permit the skull to rest in the upper one; this articulates freely with the second vertebra, thus permitting of the nodding and turning movements of the head. Besides these individual adaptations, the vertebral column, as a whole, is peculiarly adapted to pro- tect the brain from jar; this is seen in the double bend of the vertebral column and the pads of cartilage be- tween the individual vertebrae. The whole column of vertebrae joined each to the other supports the weight of the body. The largest vertebrae at the base are joined to the huge pelvic bones for the better support of the body above. That part of the vertebral column of man which bears the ribs is known as the thoracic region. The ribs, twelve in number, are long bones which combine lightness with strength; joined by elastic cartilage to the sternum in front and to the vertebrae behind, they form a wonderful protection to the organs in the thoracic cavity and j^et allow free movement in breathing. That part of the skeleton to which the bones of the anterior and posterior appendages are attached are respectively known as the pectoral girdle (from which hangs the arm) and the jpelvic girdle (which joins the leg bones to the axial skeleton). The Appendages. — The bones of the appendages attached to the pectoral and pelvic girdles are adapted peculiarly to locomo- tion and support; for this purpose the bones
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