DIGESTION 123 



Human teeth partake of both forms ; some of them are sharp, 

 and others are blunt ; they are therefore well adapted for the 

 mastication of both flesh and vegetables. Hence we infer 

 that, although man may live exclusively upon either vegetable 

 or animal food, he should, when possible, choose a diet made 

 up of both varieties. 



13. Preservation of the Teeth. In order that the teeth shall 

 remain in a sound and serviceable condition, some care is of 

 course requisite. In the* first place, they require frequent 

 cleansing; for every time we take food, some particles of it 

 remain in the mouth, and these, on account of the heat and 

 moisture present, soon begin to putrefy. This not only ren- 

 ders the breath very offensive, but promotes decay of the teeth. 



14. The saliva, or moisture of the mouth, undergoes a 

 putrefactive change, and becomes the fertile soil in which a 

 certain minute fungus has its growth. This fluid, too, if 

 allowed to dry in the mouth, collects upon the teeth in the 

 form of an unsightly, yellow concretion, called tartar. To 

 prevent this formation, and to remove other offensive sub- 

 stances, the teeth should be frequently cleaned with water, 

 applied by means of a soft tooth-brush. The prevention of 

 the tartar fungus is best effected by the use of a weak solution 

 of carbolic acid. (Read Note 1.) 



1. The Proper Care of the Teeth. " It is an important question how 

 to care for the molars. To this end the cardinal maxim is cleanliness ; 

 and again cleanliness. One means of cleansing is the natural one that 

 is, by chewing food ; for it is well known that if we have a tooth so situ- 

 ated in the jaw that it is seldom brought into use, that tooth early shows 

 signs of decay. But more effectual is the artificial means the brush. 

 Children should early be taught to use this ; and for them a softer brush 

 should be selected than for adults. They should also early be taught to 

 use no metallic substances, as pins, needles, etc., to remove substances 

 from between the teeth. The teeth should always be thoroughly cleansed 

 after taking acids into the mouth for they are the great enemies to the 

 teeth and also after candies and other forms of sugar, for theiB particles 

 that linger on the teeth are changed by decomposition into lactic acid. 

 Occasional examination of the teeth is prudent, in order that a com- 

 mencing cavity may be promptly detected and remedied. Teeth that are 



18. Cleaning of teeth ? Effects of not cleaning ? 



14. Effects of the saliva ? Formation of tartar ? How prevented ? How destroyed ? 



