Elements of histology / by E. Klein.

  • Edward Emanuel Klein
Date:
1884
Catalogue details

Licence: Public Domain Mark

Credit: Elements of histology / by E. Klein. Source: Wellcome Collection.

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    of varying length and thickness, and composed of lamellae of bone substance. According to the arrangement of the trabeculse, the spongy substance is a uniform honey-combed sub- stance, or appears longitudinally striated, as in the end of the shaft. In the latter case the marrow spaces are elongated and the trabeculse more or less parallel, but anastomosing with one another by transverse branches. 68. Development of bone.—Bone is developed in the embryo, and continues to be formed also after birth as long as bone grows, either in the cartilage, or independently of this directly from the osteogenetic layer of the periosteum. The former mode is called endochondral, the latter j^eriosteal, or intermemhranous formation. All the bones of the limbs and of the vertebral column, the sternum, and the ribs, and the bones forming the base of the skull, are preformed in the early embryo as solid hyaline cartilage, covered with a membrane identical in structure and function with the periosteum, which at a later period it becomes. The tegmental bones of the skull, the bones of the face with the lower jaw, except the angle, are not pre- formed at all. Only a membrane identical with the future periosteum is present, and underneath and from this the bone is gradually deposited. 69. Endochondral formation. — The stage next to the oiie (1) in which we have solid hyaline cartilage covered with periosteum is the following (2): Starting from the centre, or point, of ossifica- tion, and proceeding in all directions, the cartilage becomes permeated by numbers of channels (cartilage .channels) containing prolongations (periosteal processes of Yirchow) of the osteogenetic layer of the periosteum, i.e., vessels and osteoblasts, or marrow cells. This is the stage of the vascularisation of the cartilage. In the next stage (3) the cartilage bordering on these
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