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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![though they are of a different structure, and even although the circu- lation is only carried on in one of them. This disposition is not so considerable in the more perfect or complex animals, such as quadrupeds, as it is in the more simple or imperfect, nor in old animals, as in young; for the living principle in young ani- mals, and those of simple construction, is not so much confined to, or derived from, one part of the body ; so that it continues longer in a part separated from their bodies, and even would appear to be generated in it for some time; while a part, separated from an older or more perfect animal, dies sooner, and would appear to have its life entirely dependent on the body from which it was taken. Taking off the young spur of a cock and fixing it to his comb is an old and well-known experiment. I have also frequently taken out the testis of a cock and replaced it in his belly, where it has adhered and has been nourished; nay, I have put the testis of a cock into the belly of a hen with the same effecta. In like manner a fresh tooth, when transplanted from one socket to another, becomes, to all appearance, a part of that body to which it is now attached as much as it was of the one from which it was taken ; while a tooth which has been extracted for some time, so as to lose the whole of its life, will never become firm or fixed; the sockets will also in this case acquire the disposition to fill up, which they do not in the case of the insertion of a fresh tooth. These appearances show that the living principle exists in the several parts of the body, independent of the influence of the brain or circula- tion, and that it subsists by these, or is indebted to them for its con- tinuance ; and in proportion as animals have less of brain and circu- lation the living power has less dependence on them, and becomes a more active principle in itself; and in many animals there is no brain nor circulation, so that this power is capable of being continued equally by all the parts themselves, such animals being nearly similar in this respect to vegetables1*. a [These experiments are related in the Animal (Economy, see Vol. IV.] b [The practice of transplanting teeth from one person to another originated, I be- lieve, with Hunter, under whose superintendence it was frequently performed. Had the results of all these cases been known to him, it is probable that this recommenda- tion would not have been written; there is not, I believe, a single instance of its per- fect success, and there are many in which it has been followed by even fatal results. Fox, in his excellent practical work on the teeth, strongly reprobates this practice, and has probably prevented much pain and disease by exposing its continual failure, its occasional injurious results, and the want of correct feeling which seems to be neces- sarily involved in its performance. The tooth figured by Fox as having been the sub- ject of this operation is now in the collection of Guy’s Hospital; its root is deeply eroded by absorption.]](https://iiif.wellcomecollection.org/image/b21996635_0002_0076.jp2/full/800%2C/0/default.jpg)
