Anatomy, descriptive and applied / by Henry Gray.

  • Gray, Henry, 1827-1861.
Date:
1913
Catalogue details

Licence: Public Domain Mark

Credit: Anatomy, descriptive and applied / by Henry Gray. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

    38/1504 (page 42)
    lamelliE. lacunte, and canaliculi is seen, though not so plainly as in the ordinary section. The animal basis is lararely composed of ossein, or fat collagen. When boiled with water, especially under pressure, fat collagen is almost entirely resolved into gelatin. The earthy part may be obtained by calcination, in which process the animal matter is com- pletely burned out. The bone will still retain its original form, but it will be white and brittle, will have lost about one-third of its original weight, and will crumble upon the slightest pressure. The earthy matter confers on bone its hardness and rigidity, and the animal matter its tenacity. The mineral matter consists chiefly of calcium phosphate, forming about two-thirds of the weight of bone. Ossification and Growth of Bone.—For the early development of the skeleton the reader is referred to text-books on embryology. Embryonic connective-tissue cells of the meso- blast develop membrane. Membrane may become bone directly or cartilage may be deposited, which cartilage by the process of ossification is changed into bone. The tissue which is eventually to become bone contains cellular elements which evolve into osteo- blasts, or bone-forming cells. Osteoblasts exist in the connective tissues which become bone by intramem- branous ossification, and in the deeper layers of the tissue called perichondrium which invests cartilage and which becomes the osteogenetic layer of the peri- osteum. In view of the fact that in the fetal skeleton some bones are preceded by membrane (parietal bones, frontal bone, upper part of tabular portion of occipital bone, most of the bones of the face), and others are pre- ceded by rods of cartilage (the long bones), two kinds of ossification are described—viz., the intramembra- nous and the intracartilaginous. Intramembranous Ossification.—In the case of bones which are developed in membrane no cartilagi- nous mould precedes the appearance of the bone tissue. The membrane, which occupies the place of the future bone, consists of white, fibrous connective tissue, and ultimately forms the periosteum. At this stage it is seen to be composed of fibres and granular cells in a matrix. The outer portion is more fibrous, while internally the cells or osteoblasts predominate; the whole tissue is quite vascular. At the outset of the process of bone formation a little network of bony spicules is first noticed radiating from the point or centre of ossification. When these rays of Fig. 9.—Schematic diagram, showing epi- physis and diaphysis and line of ossification, Ev. Epiphysis of endochondral bone. zpt. Zone of proliferation. 7C. Zone of calcifica- tion, ca. Cartilage. (Poirier and Charpy.) Union q adjacent Fig. 10,—Part of the grow V Bony ^^^iT^ spicules. ng edge of the developing parietal bone of a fetal cat, (After J. Lawr growing bone are examined with a microscope they are found to consist at their growing point of a network of fine, clear fibres and granular corpuscles, with an intervening ground substance (Pig. 10). The fibres are termed osteogenetic fibres, and are made up of fine fibrils differing