. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Fig. 103. The condition of the jaw in old age, showing the acute projection of the chin resulting from the loss of teeth and the ab- sorption of the sockets for the teeth. Fig. 104. In toothless old age the chin and the nose tend to hob- nob together. (After Camper.) This wrecking of bone tissue already formed in order to make way for rearrangement and enlargement is accomplished by the rather large defi- nitely identified cells called osteoclasts. The des
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Fig. 103. The condition of the jaw in old age, showing the acute projection of the chin resulting from the loss of teeth and the ab- sorption of the sockets for the teeth. Fig. 104. In toothless old age the chin and the nose tend to hob- nob together. (After Camper.) This wrecking of bone tissue already formed in order to make way for rearrangement and enlargement is accomplished by the rather large defi- nitely identified cells called osteoclasts. The destructive work of these cells is not always followed by equally constructive reorganization, however, for when the work of the osteoclasts exceeds that of the osteoblasts, a bone decreases in size. Thus, in toothless old age (Fig. 103), the lower jaw not only becomes smaller through the loss of teeth, but the bony sockets in which the teeth were set also decrease in size through the removal of tissue by osteoclasts, with the result that the chin and nose tend to hobnob together (Fig. 104). ^!^___-—Spongy Bone ;^t— Compact Bone. i1?T^M- Marrow Cavity «-•'•!-~* Willi Haversian Canals----^:^^^: !^^^;^C;"0;^>^;;^j^T^V7—I nterstitia I W^^^!^')'- £• ^W La m e I lae Concentric Lamellae -^skt^ Circumferential Lamellae-' ^-^^^^ Fig. 105. Stereogram of bony 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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