OSSEOUS TISSUE. BONE. BONE SUBSTANCE.—The tissue of bone has, within the last few years, under
The general character, the varieties of I nal conformation, and the anatomical relation of bone to the contiguous textures, have been ably related in a previous article. Under the .
I present head it is proposed to treat only of the minute structure and of the developernent of bone.
For the sake of precision in the description, . the elements which conjointly form bone, or which are commonly found connected with osseous formation, will be considered under i separate heads.
1 leeted, it will be found to contain DO Ilaversian canals or corpuscles, but to be extremely thin and transparent. Such a portion, when viewed with the one-eighth of an inch object-glass of Mr. Powell's microscope, will present a deli cate granular aspect with the surface nod ulated. This granular appearance arises from the sub stance of the bone being composed of minute irregularly spherical granules. It is not diffi cult to trace this structure in any specimen of bone, though in some it is much more distinct than in others. Specimens put up in Canada balsam do not show the minute structure very well. It is best to place the object between two slips of glass with a little plain water.
A delicate spicula from the point where os sification is going on is usually very good for illustrating the granular tissue.
But the granules may be obtained separated from each other, so that each individual may be egamined apart from its fellows. NVhen so exposed to view, they exhibit a tolerably re gular diaracter, being mostly spherical, some few having an oval form. In some specimens the oval predominates over the spherical con formations. Often a few will be found which are egg-shaped, with the smaller end elongated, (see fig. 449,) though to no great extent. The osseous granules may be gained by subjecting bone to high-pressure steam, or to a red heat, till all the animal matter is removed. In either
instance the granules maybe obtained by taking a small portion of the so treated bone, satura ting it with water, and then gently reducing it to a powder between the slips of glass. 13y this manipulation die granules individually will be rendered evident when the specimen is exa mined under a high power. But, by the break ing down of the Mass, many granules are neces_LL sarily broken ; to remedy this imperfect and ea fused state of the specimen, a little dilute nuiriatic acid should be placed upon the glass in contact with the specimen. Solution of the powdered mass will instantly commence, but the broken granules will have disappeared be fore the entire ones are appreciably affected. If at this point of the experiment the acid be re moved and replaced by pure water, a perfect specimen will be gained. In examining the tissue under consideration it is most satisfactory to watclt the action of the acid upon the cal cined or steamed bone, and especially its action upon the small masses, for in these, when un dergoing the action of dilute acid, the granules composing them become particularly distinct, so that their individual character may be stu died ; and if the solvent be not removed, their separate disappeamnce may be watched as the superficial ones are exposed and acted upon by the solvent fluid. If the acid be left with the so treated bone for a sufficient length of time, all the earthy matter will be dissolved and there will remain a transparent indistinctly cellular mass, which may be supposed to be an inter gmnular substance, the purpose of which was to unite the granules into a compact whole.
Bone which has been treated with dilute acid without the previous removal of the ani mal matter, soon loses the earthy component, leaving only the animal. This, ,however, does not tend to develope the granularity; indeed it seems, in most cases, to render it less dis tinct than in either the unaltered or the calcined bone. The granules themselves are subject to some variety in size, commonly varying from the one-sixth to one-third the size of a human blood globule.