328 PHYSIOLOGY. 



have assumed their natural position. iThe second dentition 

 commences about the seventh year, and is commonly per- 

 fected before the fourteenth/ Yi % A.. * j (l ^utM^r- 



9. V^Vhen the teeth are so rnucTr crowo'ed as to'disturo 

 their regular arrangement ; or when they press so hard upon 

 each other as to destroy the enamel, one or more should be 

 removed without delay. If this precaution should be ne- 

 glected, an unsightly mal-arrangement, or inevitable destruc- 

 tion of several of the teeth, will be the melancholy result. 

 The removal of a sound tooth causes very little pain com- 

 pared with the agony attending those which are suffered to 

 become diseased. 



10. It is impossible, under ordinary circumstances, to 

 preserve the teeth for many years without keeping them 

 very clean. Food lodges between them at every meal, and 

 undergoes decomposition if not removed. A. substance, called 

 tartar, or salivary calculus, which is deposited from the 

 saliva, adheres to the teeth, becomes very hard, and finally 

 assumes a dark colour, if not constantly washed away with 

 a brush and water. If food be suffered to putrefy in spaces 

 between the teeth the process of mortification is extended to 

 the teeth themselves ; and if tartar collect in solid masses, 

 the teeth become loose in their sockets and are thus utterly 

 lost. 



11. In order to keep the teeth and gums perfectly clean 

 and healthy, it is necessary to wash them with a stiff brush 

 and water several times in a day. No person of ordinary 

 neatness would consent to eat with knives, forks and spoons, 

 unless they were cleansed after every meal. The teeth are 

 more liable to accumulate filth than any of these domestic 

 utensils, and therefore need at least equally frequent washing. 

 In the morning, after each meal, and before retiring to rest, 

 are not too many times to purify the teeth with a brush and 

 water, and once in each week with good tooth powder. 



12. The Dentifrice or Tooth Powder, which I would re. 

 commend in preference to all others which I have ever seen, 



