Teeth, a set of bones, situated in the upper and lower jaws, for the purpose of mastication: in adults, there are 32 in number, or 10" in each jaw-bone.

The teeth are of various size, being arranged in the following order: four in the front, termed cutting teet, on each side of which is a sharp-pointed, canine, or eye-tooth; adjoining to these are jive grinders on each side, the last of which is denominated the tooth of wisdom; because it seldom appears before the 25th year. The front and eye-teeth are furnished with only one root each ; the two first grinders with two; and the hindmost generally with three or four ; which may in most persons be ascertained by the number of small tubercles on the crowns.

The tooth is divided into two principal parts; namely, the crown, which projects above the gums; and the root, that is inclosed within the sockets: the crown is a hard, fine, glossy, white enamel, serving to defend the substance against external injury: the root is open at the bottom, where it is connected with vessels and nerves, by which it receives nourishment, life, and sensation.

As an account of the manner in which the teeth are formed, may prove interesting to reflecting readers, we shall proceed to state concisely the process of dentition, or teething; and conclude with a short analysis of the diseases to which these useful bones are frequently liable.

In an embryo of 3 or 4 months formation, instead of the sockets, small cells are observable: these are separated by thin membranes, each of which progressively exhibits a vascular bag, containing a soft knob, that is covered by the rising tooth, forming a hard coat; but the enamel appears to originate from crystallized matter. During the first year, the two middle front teeth in the under jaw, and shortly after, the two upper ones, become visible: they are succeeded by the foremost front teeth. In the commencement of the second year, the first grinder, on each side, grows successively in the under and upper jaws: the next in rotation, are the canine or corner teeth, and finally, about the third year, there rise from two to three grinders on each side. About the seventh year, all these teeth are, by an effort of Nature, gradually replaced by a new set, to which are joined, in the tenth or eleventh year, another grinder, and, at a later period, the tooth of wisdom.

During the progress of dentition, children are subject to various affections, such as convulsions, in-flammation, fever, etc. occasioned by the pressure of the teeth, in bursting through the gums. At this period, a moderate looseness, or a copious flow of saliva are, in general, favourable signs. With a view to promote the latter, it will be advisable to let the child chew or gnaw such substances, as have a tendency to mollify the gums, and, by their pressure, to facilitate the protrusion; for which purpose a piece of liquorice or marshmallow root, etc. will be of service; or, the gums may be softened and relaxed, by rubbing them with sweet oil, honey, or other emollients. - Costiveness should be removed by mild aperient clysters. If, however, all these endeavours prove ineffectual, relief has often been derived from an incision made in the gum ; though such operation should be undertaken only by the surgeon. - In cases of extreme weakness the application of blisters behind the ears, or to the back, will prove beneficial; and, as distressing symptoms frequently arise from crudities and obstructions in the first passages, it will be necessary to attend to this circumstance: thus, if the child be troubled with acidity and flatulence, the testaceous powder, or calcined magnesia with a few grains of rhubarb, mixed with powder of sweet fennel-seeds, will form a very useful remedy ; or, when worms torment the infant, the means suggested under that article, should be speedily adopted. - On this occasion, we deem it our duty, in the strongest terms to caution parents against the use of laudanum, and other composing medicines, especially when the bowels are obstructed.

With respect to the diseases of the teeth, we shall, in this place, mention only such as occur more frequently, and which are, by proper attention, or by external applications, easily removed. - From a view of the nature and formation of the teeth, it must be evident, that whatever may tend to remove the enamel, for instance, acrid dentifrices and tinctures, hard metallic tooth-picks, sudden changes from heat to cold (especially in taking food), by exposing the nerve, cannot fail to produce the tooth-ach; and, in the course of time, a decay of the bone itself. There are even instances, where such corruption, unless timely checked, has extended its influence to the jaw-bone. Nothing, however, contributes to injure them more certainly than uncleanliness ; by which a kind of tartar is generated, that settles on the teeth, and separates them from the gums : thus, the air and the food coming into immediate contact with the bony substance, will prove a never-failing source of pain and distress.

Cure: - As it would be a vain attempt to point out any specific, by which the tooth-ach can be removed, we shall recommend only such remedies as are adapted to the several causes, from which it may originate. - If the patient be of a plethoric habit, or the gums be considerably inflamed, recourse should be had to bleeding, particularly by leeches and cupping-glasses, applied contiguously to the part affected: next, blisters behind the ears, or on the nape of the neck, will be found of service. - Dr. Cullen recommends vitriolic aether to be dropped on the cheek, and to hold the hand on the part, till that volatile liquor be evaporated. Should, however, the pain still continue, without intermission, a few drops of laudanum on cotton, laid on the tooth, will sometimes afford relief. Where the bone is hollow, and decayed, it will be advisable either to have it drawn by an able dentist, or to resort to such substances as destroy the nerve: the latter object may be effected by a careful application of the strong mineral acids, juniper-oil, or by a red-hot wire; but this operation, which has frequently produced the desired effect, ought never to be entrusted to an unskilful person. - As the tooth-ach is frequently induced by cold, and attended with symptoms of Catarrh, it will in such cases be requisite to follow the directions given in that article. - This complaint, likewise, often proceeds from affections or debility of the stomach ; a source which may be ascertained by the symptoms of indigestion, such as loss of appetite, nausea, vomiting, and head-ach, with this peculiar circumstance, that the pain generally returns at regular periods. In such case, relief can only be expected from a proper use of emetics, and mild aperients, succeeded by a judicious course of the Peruvian bark, and similar tonics.

Another source of these affections, is an irregular disposition, or arrangement, especially of the front-teeth, and mostly in the second set. It may proceed either from some of the first set having been suffered to remain in the jaw, after the second has appeared ; from a want of space in the jawbone, or, from mal-conformation. In these cases, the only effectual remedy is that of extracting such of the teeth, as by their situation obstruct their neighbours, and sometimes occasion considerable distress.

If the teeth should be loosened by external violence, they may again be fixed, by pressing them firmly into the sockets, and preserving them in that situation, either by a silk, or other ligature attached to the adjoining tooth: the patient, however, ought to subsist entirely on spoon-meat, or other soft and liquid food, till the desired effect be attained. But, where this separation arises from a sponginess or weakness in the gums, mild astringents, for instance, a solution of alum and sugar, tincture of bark, catechu, etc. will serve to consolidate the surrounding parts.

For cleansing and preserving the teeth, burnt bread, or bark, applied by the small ringer, or on a piece of calico, will be found a safe and useful dentifrice. - Lord Dundonald recommends, for this purpose, a weak solution of Soda.

Lastly, in cases where a substitution of artificial teeth should be deemed necessary, these useful bones ought to be manufactured from the tooth of the Hippopotamus, or river-horse; and on no account whatever to be taken from other persons. There are instances on medical record, where the latter practice has communicated in-fectious diseases, and eventually proved fatal.