Licence: Public Domain Mark
Credit: The works of John Hunter. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![ture has taken care that the bottom part of the cavity should he filled up by new matter in proportion as the surface of the teeth is worn down. This new matter may be easily known from the old, for when a tooth has been worn down almost to the neck, a spot may always be seen in the middle, which is more transparent, and at the same time of a darker colour (occasioned in some measure by the dark cavity under it), and generally softer than the other*. Any person may be con- vinced of thetruth of these observations by taking two teeth of the same class, but of very different ages, one just completely formed, the other worn down almost to its neck. In the last he will observe the dark spot in the centre, and if as much is cut off from the complete tooth as has been worn off from the old one, the cavity of the young tooth will be found cut through; and on examining the other, its cavity will be found filled up below that surface. Now this observation contra- dicts the idea of the hole leading into the cavity of the tooth being closed up ; and what is still a further proof of it, I have been able to in- ject vessels in the cavities of the teeth in very old people when the al- veolar process has been gone, and the teeth very loose in the gum. Old people are often found to have very good sets of teeth, only pretty much worn down. The reason of this is, that such people never had any disorder in their teeth, or alveolar processes, sufficient to oc- casion the falling of one tooth. For if by accident one tooth is lost, the rest will necessarily fail in some degree, even though they are sound, and likely to remain so, had not this accident happened ; and this weak- ening cause is greater in proportion to the number that are lost. From this observation we see that the teeth support one another3. Of the Continual Growth of the Teeth. It has been asserted that the teeth are continually growing, and that the abrasion is sufficient to keep them always of the same length; but * PI. V. f. 25, 26. 3 [The filling up of the internal cavity of the teeth in old people here alluded to, ap- pears to be consequent upon the loss of substance from the surface. As the superstra- tum of bone becomes thinner by abrasion, the membrane lining the internal cavity, from which, as I have before shown, the hone of the tooth ivas originally produced, now again resumes its ossific action, and produces a fresh layer of bony matter, which in some cases at length fills the socket, and obliterates the membrane from which it has been secreted. This is particularly the case in sailors who have lived much upon hard biscuits, a circumstance which tends greatly to accelerate this abrasion of the surface, a process perfectly and obviously analogous to that of the wearing of the teeth in grami- nivorous animals.]](https://iiif.wellcomecollection.org/image/b21996635_0002_0068.jp2/full/800%2C/0/default.jpg)
