A system of dental surgery / by Sir John Tomes.

  • John Tomes
Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: A system of dental surgery / by Sir John Tomes. Source: Wellcome Collection.

    107/808 page 91
    been expected, take i)lace in direct continuation (jf its previous course; but, in obedience to a law ah-eudy alhided to (page 14), gives to the added portion of canal an upward and backward direction. Tiiis fresii addition to tlie canal therefore forms witiiin tlie thickness of tiie jaw an angle with that previously existing, and this angle corresponds in position with the opening ov mental foramen in the fa'tal jaw. If then we rasp off the surface till we reacli this angle, and take <nir measurements from it instead of from the external opening, we siiall have an unchanging point, and the I'esults of our incpur}' will be consistent witii tiiose attained wiien tiie tubercles were cliosen as tlie fixed points. In old age natin-e ])erfornis this operation for us, and removes the bone till this angle is nearly, or (piite, reached—hence the foramen is brought down nearer to the hjwer border of the jaw. ISut with the exception of additions to either end during the period of growth ami consei[uent alterations the aperture, there is not the smallest reason to suppose that the ])ositiou of the canal is in any way changed at any period of develop- ment. In the former editions of this work certain actual measure- ments of a particular series of jaws were given ; but as I have foiuid that students have experienced some little ilitiieulty in grasping the meaning of the passage when placed Ijefore tiiem in this form, it has seemed preferable to embody the results of these investigations in the accompany- ing diagrams. As some variations, due to individual peculiarities, such as greater less development of the chin, exist between different specimens, these diagrams are drawn up according to average dimensions taken from a considerable niunber of jaws, and are drawn to scale. The hoi'i/<Jutal line represents the level of tiie anterior p<n'tion of tlie iufo'ior dental canal in tiie feetus, and the corresponiling portion in the adult jaw, which maybe tidcen as separating tiie alveolar portion, strictly suliservient to
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