Volume 1

The American system of dentistry / in treatises by various authors ; edited by Wilbur F. Litch.

Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: The American system of dentistry / in treatises by various authors ; edited by Wilbur F. Litch. Source: Wellcome Collection.

    26/1038 page 36
    The outer or compact portion is hard and ivory-like in texture, giving rigidity and firmness to the shaft. In long bones the compact substance is thickest in the centre of the diaphysis, gradually growing thinner toward the ends, the fibres running longitudinally. The inner, spongy, or cancellated portion is softer than the outer covering, and is made up of slender bars and thin lamella, which cross each other in various directions (see a a, b b, e c, Fig. 2), and produce Fig. 1. Section of a Sound Adult Femur. Fig. 2. of the Femur. an open structure having a reticular appearance, so arranged as to form an internal support to the outer portion of the bone. This formation is specially marked in the upper end of the femur. The cancellated portion is found in greatest quantity at the ends of long bones, at which position the surfaces are enlarged for purposes of articulation. It is the more vascular portion of bone; adds bulk with- out greatly increasing weight ; acts as a cushion to articulating surfaces; and by its elastic properties modifies the force of concussion. The flat bones, such as those found in the skull, furnish surfaces for the more convenient attachment of ligaments, muscles, and tendons. They are composed of two tables, an outer and an inner, with the cancellated portion (diploe) between. The cancellar substance of bones generally, but especially in those of the cranium, is pervaded by irregular canals for the accommodation of blood-vessels. The two plates or tables of flat bones are bound together by the cancellated tissue, which not only helps to resist fracture, but acts as a cushion, deadening the force of shock by distributing it over larger surfaces, thus in great measure preventing injury to the brain: it also combines great strength with lightness of weight. If a close examination is made of a specimen, as shown in Fig. 1, by the aid of a magnifying-glass, it will be found that the compact tissue is porous in a greater or less degree, its density depending upon the
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