

TKETH. 



met imes not appearing till late in lid', 

 is called u-isdom-ttwlh. The variation in the num- 

 ber of teeth usually depends on these wisdom-teeth. 



The danger to which children are exposed dur- 

 ing thf time of dentition, arises from the pressure 

 ot the teeth in the gum, so as to irritate it, and 

 excite pain and inflammation. The effect of this 

 irritation is, that the gum wastes, and becomes 

 gradually thinner at this part, till, at length, the 

 tooth protrudes. In such cases, therefore, we 

 may, with great propriety, assist nature by cutting 

 the gum. These teeth are twenty in number, and 

 are called temporary or milk teeth, because they 

 are all shed lift ween the age of seven and fourteen, 

 and are supplied by others of a firmer texture, with 

 large fangs, which remain till they become affected 

 by disease, or fall out in old age, and are therefore 

 called the permanent, or adult teeth. Besides 

 these twenty teeth, which succeed the temporary 

 ones, there are twelve others to be added to make 

 up the number thirty-two. These twelve are 

 three grinders on each side in both jaws ; and in 

 order to make room for this addition, we find the 

 jaws grow as the teeth grow, so that they appear 

 as completely filled with twenty teeth, as they are 

 afterwards with thirty-two. Hence, in children, 

 the face is flatter and rounder than in adults. The 

 denies sapientite, or wisdom-teeth, do not pass 

 through the gum till between the age of twenty 

 and thirty. They have, in some instances, been 

 cut at the age of forty, fifty, sixty, and even eighty 

 years; and sometimes do not appear at all. Some- 

 times, likewise, a third set of teeth appears, about 

 the age of sixty or seventy. 



The teeth are subject to a variety of accidents. 

 Sometimes the gums become so affected as to occa- 

 sion them to fall out ; and the teeth themselves 

 are frequently rendered carious by causes which 

 have not hitherto been satisfactorily explained. 

 The disease usually begins on that side of the 

 tooth which is not exposed to pressure, and gra- 

 dually advances till an opening is made into the 

 cavity : as soon as the cavity is exposed, the tooth 

 becomes liable to considerable pain, from the air 

 coming into contact with the nerve. The enamel 

 of the teeth, as we have already said, is very hard, 

 but liable to be cracked by the pressure of very 

 hard substances, or by exposure to great heat or 

 cold, and, more peculiarly, by sudden changes from 

 one to the other. The bony substance below, 

 being thus exposed, begins to decay ; the nerve 

 and blood-vessels are at length laid bare, and tooth- 

 ache ensues. Rheumatism, gout, and venereal dis- 

 orders exert a very prejudicial influence on the 

 teeth. To preserve the teeth, we must guard 

 against too hot or too cold drinks ; violent changes 

 of temperature ; biting of very hard substances, 

 as in cracking nuts, also biting off threads, and 

 untying knots with the teeth, as the former injures 

 the enamel, the latter tends to loosen the teeth in 

 their sockets. Acids, of all sorts, particularly the 

 stronger ones, injure the enamel. Therefore, all 

 tooth-washes which contain them are eventually 

 prejudicial to the teeth, although the immediate 

 effect is to clean and whiten them. Rough-pointed 

 substances also injure the enamel, so that we 

 should avoid the" use of metallic tooth-picks, and 

 tooth-powder made of pumice stone, coral, cream 

 of tartar, &c. People who eat much meat and 

 little bread, or have a bad digestion, or smoke 

 tobacco, find that a deposit of earthy particles col- 

 lects around the teeth, and forms tartar, particu- 



larly about the parts which lire least exposed to 

 the action of the food the lower and im.er parts, 

 near tin- gums. The gums gradualh separate from 

 the teeth ; the consequence is, that tlu>e decay, 

 and the breath is rendeied oH'ensive. To avoid 

 these effects, the teeth should be daily cleaned with 

 tepid water and a hard brush. A proper powder 

 should also be occasionally applied to them. Where 

 tartar has been formed, it should be removed by the 

 dentist, and its return carefully guarded against. 

 Decay can often be checked by the removal of the 

 parts which have turned blaek, and filling the cavi- 

 ty with gold, so that the teeth may be preserved 

 i'or many years or for life. Every one should have 

 his teeth examined at intervals of a few months, to 

 detect incipient decay. 



Artificial teeth are often inserted to remedy, as 

 far as possible, the loss of the natural ones. These 

 were formerly taken from the corpses of healthy 

 men (though this point of healthiness was often far 

 too little attended to) : they are now, more gene- 

 rally, prepared from the teeth of the walrus, or sea- 

 cow, from ivory, from porcelain, &c. Artificial 

 teeth are either secured in the stumps of natural 

 ones, by means of a gold or silver support, or, where 

 such stumps do not exist, they are fastened to 

 neighbouring teeth by gold or silk thread. The 

 porcelain teeth have an advantage over the other 

 kinds, which lose their colour, and acquire a dis- 

 agreeable smell in the course of time. Their hard- 

 ness may perhaps, however, make them injurious to 

 the contiguous natural teeth. Besides the acciden- 

 tal means by which the teeth are affected, old age 

 seldom fails to bring with it sure and natural causes 

 for their removal. The alveoli fill up, and the teeth 

 consequently, fall out. The gums then no longer 

 meet in the fore part of the mouth, the chin pro- 

 jects forwards, and, the face being rendered much 

 shorter, the whole physiognomy appears considera- 

 bly altered. 



The great variety in the structure of the human 

 teeth, fits us for a variety of food, and, when com- 

 pared with the teeth given to other animals, may, 

 in some measure, enable us to explain the nature of 

 the aliment for which man is intended by nature. 

 Thus in ruminating animals, we find incisors only 

 in the lower jaw, for cutting the grass, and molars 

 for grinding it ; in graminivorous animals, we see 

 molars alone: and in carnivorous animals, canine 

 teeth for catching at their prey, and incisors and 

 molars for cutting and dividing it. But as man is 

 not designed to catch and kill his prey with his teeth, 

 we observe that our canine are shaped differently 

 from the fangs of beasts of prey, in whom we find 

 them either longer than the rest of the teeth, or 

 curved. The incisors, likewise, are sharper in those 

 animals than in man. Nor are the molars in the 

 human subject similar to the molars of carnivorous 

 animals ; they are flatter in man than in these ani- 

 mals; and in the latter, we likewise find them 

 sharper at the edges, more calculated to cut and 

 tear the food, and, by their greater strength, capa- 

 ble of breaking the bones of animals. From these 

 circumstances, therefore, we may consider man as 

 partaking of the nature of these different classes ; 

 as approaching more to the carnivorous than to the 

 herbivorous tribe of animals; but upon the whole 

 formed for a mixed aliment, and fitted equally to 

 live upon flesh and upon vegetables. Those philo- 

 sophers, therefore, who would confine a man wholly 

 to vegetable food, do not seem to have studied na- 

 ture. As the molars are the last teeth that are 



