File:Hand-book of physiology (1892) (14578502889).jpg

Identifier: handbookofphysio00bake (find matches)
Title: Hand-book of physiology
Year: 1892 (1890s)
Authors: Baker, W. Morrant, (William Morrant), 1839-1896 Harris, Vincent Dormer Kirkes, William Senhouse, 1823-1864. Hand-book of physiology. 13th ed
Subjects: Physiology Human physiology
Publisher: London : John Murray
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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um or periosteum) ;but in the developmentof such a bone as thefemur, which may betaken as the type ofso-called ossification incartilage, lime-salts arefirst of all deposited inthe cartilage ; this cal-cified cartilage, however,is gradually and entirelyre-absorbed, being ulti-mately replaced by boneformed from the perios-teum, till in the adultstructure nothing buttrue bone is left. Thus,in the process of ossi-fication in cartilage, calcification of the cartilaginous matrixprecedes the real formation of bone. We must, therefore, clearlydistinguish between calcification and ossification. The former issimply the infiltration of an animal tissue with lime-salts, andis, therefore, a change of chemical composition rather than ofstructure ; while ossification is the formation of true bone—atissue more complex and more highly organised than that fromwhich it is derived. Centres of Ossification.—In all bones ossification com-mences at one or more points, termed centres of ossification. The
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Fig. 71.—Transverse section of femur of a humanembryo about eleven weeks old. a, rudimentaryHaversian canal in cross section; b, in longi-tudinal section; c, osteoblasts ; d, newly formedosseous substance of a lighter colour; e, that ofgreater age; /, lacunae with their cells ; g, a cellstill united to an osteoblast. (Frey.) 72 STRUCTURE OF THE ELEMENTARY TISSUES, (ch. ill. long bones, e.g., femur, humerus, <fec, have at least three suchpoints—one for the ossification of the shaft or diaphysis, and onefor each articular extremity or epiphysis. Besides these threeprimary centres which are always present in long bones, varioussecondary centres may be superadded for the ossification ofdifferent processes. Growth of Bone.—Bones increase in length by the advanceof the process of ossification into the cartilage intermediatebetween the diaphysis and epiphysis. The increase in lengthindeed is due entirely to growth at the two ends of the shaft.This is proved by inserting two pins int

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