The principles and practice of dentistry : including anatomy, physiology, pathology, therapeutics, dental surgery and mechanism / by Chapin A. Harris.

  • Harris, Chapin A. (Chapin Aaron), 1806-1860.
Date:
1882
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Licence: Public Domain Mark

Credit: The principles and practice of dentistry : including anatomy, physiology, pathology, therapeutics, dental surgery and mechanism / by Chapin A. Harris. 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.

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    mass of germinal matter, surrounded by a thin layer of soft formed material with which it is continuous, and which passes uninterrupt- edly into the hard calcified formed material. This hard formed ma- terial is everywhere perforated by little channels called canaliculi, along which the nutrient nuiterial is conveyed to the germinal matter. These canaliculi are formed in a manner corresponding to the deposi- tion of the mineral matter, that is, from without inward, commencing at a point most distant from the germinal matter. In the dried bone these canals are seen to communicate with little vacant spaces called lacunae, occupied in the fresh state with germinal matter, seeming to associate them one with another. In this manner, each lacuna com- municates freely with adjacent lacunce. The only part of the bone, in Dr. Beale's opinion, which can be said to be living, is the nucleus or bone cell in the space or lacuna, constituting perhaps one-twelfth part of the bone; all the rest being as dead in the living body as when removed from it. It (the germi- nal matter) alone can grow and give rise to the formation of matrix. Bone cannot produce hone, but the germinal matter of bone may become converted into new hone tissue. Virchow is of the opinion that the matrix is true intercellular substance into which proceed stellate pro- cesses from the cells occupying the lacunse, thus giving rise to the canaliculi; an opinion directly opposite to that of Dr. Beale, that the canaliculi begin in the matrix (which is not formed independently of the cell, but consists simply of the formed material, or cell wall, in which mineral matter has been deposited,) and extend to the germinal matter occupying the lacuna! space. This germinal matter is always present in the lacuna ; on it depends the circulation of the calcareous matter held in solution by the blood ; without it bone tissue cannot be formed, and on its presence the life of the bone depends. The canaliculi, then, are the altered spaces or ducts which are left between the calcare- ous globules originally deposited, and through them pass fluids to and from the germinal matter. (Beale On the Structure and Growth of Tissues, 128.) Originally triangular in form, they finally become so altered by the filling up of the angles as to exhibit a circular ajipearance on ti'ansverse section. The osseous tissue with its canaliculi and germinal matter always bears a fixed and definite relation to the vessels. It may exist as solid cylindrical processes covered with a vascular mem- brane, or as thin laminae also covered with a vascular membrane, or as concentric laminae arranged round a central opening, a Haversian canal. Each Haversian canal has a diameter of about one-five- hundredth of an inch; though they are of very different sizes, varying from one-fifteen-hundredth to one-two-hundredth of an inch in diameter. The elementary parts of bone are so arranged as to form either the