. The development of the chick : an introduction to embryology. Embryology; Chickens -- Embryos. THE SKELETON 409 day in the femur of the chick. The process extends towards the ends, and faster at the periphery of the cartilage (, next to the perichondral bone) than in the center. In this way there remain two terminal, cone-shaped cartilages, and the ends of the cones project into the marrow cavity (Fig. 231 A). (3) Calcification of Cartilage. Salts of lime are deposited in the matrix of the cartilage at the ends of the marrow cavity; such cartilage is then removed by osteoclasts, large mu
. The development of the chick : an introduction to embryology. Embryology; Chickens -- Embryos. THE SKELETON 409 day in the femur of the chick. The process extends towards the ends, and faster at the periphery of the cartilage (, next to the perichondral bone) than in the center. In this way there remain two terminal, cone-shaped cartilages, and the ends of the cones project into the marrow cavity (Fig. 231 A). (3) Calcification of Cartilage. Salts of lime are deposited in the matrix of the cartilage at the ends of the marrow cavity; such cartilage is then removed by osteoclasts, large multinu- cleated cells, of vascular en- dothelial origin, according to Brachet (seventeenth or eigh- teenth day of incubation). (4) Endochondral Ossifi,ca- tion. Osteoblasts within the marrow cavity deposit bone on the surface of the rays of cal- cified cartilage that remain between the places eaten out by osteoclasts, and on the inner surface of the perichon- dral bone. These processes gradually extend towards the ends of the bone, and there is never any independent epiphysial center of ossification in long bones of birds, as there is in mammals. The ends of the bones remain cartilaginous and provide for growth in leiigth. Grow^th in diameter of the bones takes place from the periosteum, and is accompanied by enlargement of the marrow^ cavity, owing to simultaneous ab- sorption of the bone from within. It is thus obvious that all of the endochondral bone is removed from the shaft in course of time; some remains in the spongy ends. The details of the process of ossification will not be described here, and it only remains to emphasize a few points. At a stage shortly after the beginning of absorption of the cartilage in the. Fig. 231 A. — Longitudinal section of the femur of a chick of 196 hours' in- cubation ; semi-diagrammatic. (After Brachet.) art. Cart., Articular cartilage. C. C, Calcified cartilage, end. B., Endochon- dral bone. M., Marrow cavity. P'ch., Perichondrium. P'o
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Keywords: ., bookauthorlilliefrankrat, bookcentury1900, booksubjectembryology
