. The comparative anatomy of the domesticated animals. Veterinary anatomy. 20 THE BONES. masses forms layers of bone substance, that finish by constituting the lamellaB of spongy tissue at the periphery and medullary tissue at the centre, to fill the areola of the latter. In this way is accomplished the transformation of cartilage into bone. As will have been observed, it is not a mere calcification of the cartilaginous tissue, «^A, but a real substitution of bone tissue, presentmg the following phases : 1. Peri- tijfe*^-, ( chondrial and endochondral calcification in places (nuclei or centre
. The comparative anatomy of the domesticated animals. Veterinary anatomy. 20 THE BONES. masses forms layers of bone substance, that finish by constituting the lamellaB of spongy tissue at the periphery and medullary tissue at the centre, to fill the areola of the latter. In this way is accomplished the transformation of cartilage into bone. As will have been observed, it is not a mere calcification of the cartilaginous tissue, «^A, but a real substitution of bone tissue, presentmg the following phases : 1. Peri- tijfe*^-, ( chondrial and endochondral calcification in places (nuclei or centres of ossifica- tion). 2. Invasion of the centres of ossification by vessels, rivulation of the cartilage. 3. MedulHzation of the cartilage, and formation of^ osteoblasts. 4. Development of the 'Jt^ <^^ .^^^ â '⢠'â " bone tissue, appearance of the osteoplasts. J"^ ^§ e^^ /^:r^ B. Development of the Fibrous Bones.âThe bones originally fibrous are not merely charged with lime salts in order to acquire a bony appearance. They do not pass through a transitory cartilaginous state, but the phenomena of ossification take place in the fibrous tissue in the following manner :â The fasciculi of connective tissue become calcified, separate here and there from one another to form spaces, into which blood-vessels enter or osteoblasts appear. To this phase of medullization succeeds the phase of ossification, which is accomplished in the same manner as in the cartilaginous bones. Only the directing lines are represented by connective fasciculi, which later become Sharpey's fibres. 0. Progress of Ossification.âOssification com- mences simultaneously in several parts of the skeleton, and in each of the bones in particularâthough not throughout their entire extent at the same time. On CARTILAGE AT THE SEAT OF thc coutrary, lu certain determinate points of the carti- ossiFicATioN, showing at its lagiuous or fibrous mass, osseous tissue is developed ir^'lsCi:;...'":
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