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, inflammation, fever, &c. 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, &c. 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,
