62 PHYSIOLOGY AND TEMPERANCE. 



growing tooth presses against the milk tooth, loosening and 

 crowding it up, until it finally drops out. Sometimes the 

 milk teeth remain firm in their sockets, and if not removed 

 the coming teeth will be pressed aside, causing unsightly 

 irregularities. 



6. Care of the Teeth. When a permanent tooth is 

 removed, another does not come in its place. Constant atten- 

 tion is necessary to preserve the teeth from decay. The prin- 

 cipal source of danger is from particles of food getting lodged 

 between them. If allowed to remain, the food decomposes, 

 and destroys the enamel, causing ulceration around the body 

 of the tooth. To prevent this, the tooth-brush should be used 

 daily, and all food removed from between the teeth. When 

 carefully attended to in this way, tooth powder and servere 

 scouring of the teeth are not necessary. In fact, the enamel 

 may be injured by too much interference. 



A deposit from the saliva, called tartar, often forms around 

 the root of the tooth. This should be removed, or it may 

 extend toward the root and loosen the tooth; or decomposing, 

 it may injure or discolor the enamel. It is very often the 

 decomposition of the tartar, or of bits of food, which gives 

 rise to foulness of breath. Decay of the tooth may arise 

 from injury to the enamel by biting substances too hard for 

 the teeth, such as bending a pin or cracking nuts. The 

 enamel may also be cracked by sudden exposure to cold. 

 The mouth should be kept closed on going out of a warm 

 room into the wintry cold. If the enamel is preserved un- 

 broken, the tooth is not likely to decay. 



Human teeth loosen and drop out in advanced age. The 

 wisdom teeth, so called because they do not appear until 

 maturity, the " age for wisdom," are usually the first to dis- 

 appear. The structure of a tooth is so hard and compact, 

 that long after death, when the bones of the body have all 

 crumbled to dust, the teeth remain whole. 



