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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![marks of being vascular and of having a circulation of fluids : the most subtile injections we can make never reach it; it takes no tinge from feeding with madder, even in the youngest animals; and, as was ob- served above, when soaked in a gentle acid there appears no gristly or fleshy part with which the earthy part had been incorporated*. We shall speak of the use and formation of the enamel hereafter, when they will be better understooda. Of the Bony Part of a Tooth. The other substance of which a tooth is composed is bony, but much harder than the most compact part of bones in general. This substance makes the interior part of the body, the neck, and the whole of the root of a tooth. It is a mixture of two substances, viz. calcareous earth and an animal substance, which we might suppose to be organized and vas- cular. The earth is in very considerable quantity : it remains of the same shape after calcination, so that it is in some measure kept together by cohesion; and it is capable of being extracted by steeping in the muriatic and some other acids. The animal substance, when deprived away, from one end to the other, then burn it gently in the fire ; after this is done, wash the filed surface with an acid, or scrape it with a knife. By this method you will clean the edge of the enamel, which will remain white, and the bony part will be found black. * In all these experiments I never could observe that the enamel was in the least tinged, either in the growing or formed tooth. This looks as if the enamel were the earth more fully depurated, or strained off, from the common juices in such a manner as not to allow the gross particles of madder to pass. Here it may not be amiss to remark, that the names given to animal substance, such as gluten, &c., are not in the least expressive of the thing meant, for there is no such thing as glue in an animal till it has either undergone a putrefactive process or been changed by heat. And here, too, I wish it to be understood that I do not consider earth as any part of an animal, or that it makes up any part of an animal substance. B [The structure of the enamel is perfectly crystalline. The crystals are fibrous in appearance, and placed parallel to each other, at right angles with the surface of the bony portion of the tooth with which their inner terminations are placed in contact. It is true that there is a trace of animal matter in this substance, according to the follow - ing analysis by Berzelius: Phosphate of lime 85'3 Fluate of lime 3’2 Carbonate of lime 8* Phosphate of magnesia 1*5 Soda and muriate of soda ... 1* Animal matter and water ... 1* 100]](https://iiif.wellcomecollection.org/image/b21996635_0002_0036.jp2/full/800%2C/0/default.jpg)
