application of acrid matter does not always excite a pain in the tooth itself, or an inflammatory affection of the neighbouring parts; but that it very often operates by producing a diathesis only; so that cold applied to the neighbouring parts does excite both a pain in the tooth, and an inflammatory affection of the neighbouring parts which did not appear before.

There seem to be also certain states of the body, which operate upon the same diathesis, so as to produce toothach. Such seems to be the case with pregnant women, who are more liable to toothach than other women. There are probably also some cases of increased irritability which render persons more subject to toothach. Thus women are more liable to the disease than men, and particularly women liable to hysteric affections.

482. The acrid matter producing this disease seems to be generated first in the hard substances of the teeth; and as it often appears first upon the external surface of these, it might be suspected to arise from the application of external matters to the teeth: but as the production of this acrimony is often begun in the internal cavity of the teeth, where the operation of external matters cannot be suspected, and as even when it begins upon the external parts of the teeth, the operation of the cause is at first in a small portion of the teeth only, it is difficult to suppose that any matter

externally applied could act in such a partial manner; so it is presumed that the acrid matter occa. sioning the toothach is produced by some vice originating in the substance of the tooth itself. When it begins upon the external surface, it is on the enamel; but upon the internal surface, it must be in the bony part. From what causes it arises in either of these substances, I do not at all know; but I suspect that it often arises from some more general fault in the fluids of the body. The frequent use of mercury, especially when thrown much upon the mouth, and the state of the fluids in scurvy, seem both of them to give a disposition to a caries in the teeth; and it is possible that some other acrimonious states of the fluids may have the same effect.

483. A caries in some part of the teeth, whether arising upon their internal surface or upon their external, proceeding so far as to reach the nerves in the cavity of the teeth, is pretty manifestly the cause of toothach, and of the first attacks of it but when the cavity of the teeth has been opened, so that the external air or other matters can reach that cavity, these are often the exciting causes of toothach, and serve to prove in general, that acrid matters applied to the nerves occasion the disease.

484. What is the nature of the matter produced

in the caries of the teeth, I do not understand, nor have I found any proper corrector of it; but I presume it to be of the putrid kind, as it often taints the breath with a fetid odour.

485. In the cure of this disease, a long experience has shewn, that the extraction of the carious tooth proves the most effectual, and very often the only effectual remedy of the disease. But as in some cases this extraction is not proper, and as in many cases it is obstinately avoided, other means of curing the disease, or at least of relieving the pain, have been sought for and much practised.

486. Among these remedies, those are likely to be the most effectual which entirely destroy the affected nerve, or at least so much of it as is exposed to the action of the acrid matter in the tooth. When an opening is made into the cavity of the tooth, the nerve of it may be destroyed most certainly by the actual cautery; and it may also possibly be done by the application of potential caustics, either of the alkaline or acid kind.

487. When these remedies cannot be rendered effectual, relief may often be obtained by diminishing the sensibility of the nerve affected, by the application of opium, or of the more acrid aromatic oils, directly to the nerve in the tooth. It appears also, that the sensibility of the affected nerve may

often be for some time diminished by the external application of opium to the extremities of those nerves in the skin, which are branches of the same fifth pair of nerves with those of the teeth.

488. When the disease consists entirely in a pain of the nerve of the tooth, without any considerable affection communicated to the neighbouring parts, the remedies already mentioned are those especially to be employed; but when the disease consists very much in an inflammatory affection of the muscles and membranes of the jaw, and when at the same time there is little or no access for the above-mentioned remedies to the affected nerve, other measures are to be employed for relieving the disease.

489. If the disease be attended with any general phlogistic diathesis of the system, or with any considerable degree of pyrexia, a general bleeding may be useful in relieving the disease; but these circumstances occur very rarely, and the disease is for the most part a purely topical affection; in which, as I observed before, a general bleeding is of very little service. As this disease, however, is a topical inflammation, it might be supposed that topical bleedings would be very useful, and sometimes they are so; but it is seldom that their effects are either considerable or permanent. The reasons of this I take to be, that the disease does

not consist in an affection of the blood-vessels alone, as in the ordinary cases of rheumatism; but in a peculiar affection of the fibres both of the muscles and of the vessels of the part induced by irritation. The inefficacy of topical bleedings is with me a proof of the disease being of the latter kind.

490. The remedies therefore necessary to give relief in this disease, are those which take off the spasm of the vessels, and especially of the muscles and membranes affected. Such are blistering, brought as near to the part affected as can conveniently be done; and such are also increased excretions excited in the neighbouring parts, as of the saliva and mucus of the mouth by the use of acrid masticatories. It is often sufficient to excite a strong sensation in the neighbouring parts; as by eau de luce, spirit of lavender, or Hungary water, snuffed up the nostrils; or by the vitriolic æther properly applied to the cheek. It is upon the same footing that I suppose brandy or other ardent spirit held in the mouth is often of service.

491. There are cases of toothach in which it does not appear that the disease arises from an acrid matter immediately applied to the nerve of a tooth; but from the external application of cold, or some other causes immediately applied to the muscles and membranes of the jaw; and which