DENT 



1768 



DENTISTRY , 



Multiplication: 



The average weight of the girls in a dass of 

 25 is 86 Ib. 9 oz. What do they all weigh? 

 Ib. oz. 



86 9 



. 25 



2150 Ib. 225 oz. = 2164 Ib. 1 oz. 



Multiply 9 ounces by 25 and get 225 ounces; 

 multiply 86 pounds by 25 and get 2150 pounds. 

 Change 225 ounces to pounds by dividing 225 by 

 16 (the number of ounces in a pound). Find 

 225 ounces zr 14 pounds and 1 ounce, and note 

 that the answer becomes 2164 pounds and 1 

 ounce. 



Division: 



yr. 



6|3 



mo. 

 8 



da. 



20 



7 mo. 



Note 3 yr. = 36 mo. 36 mo. + 8 mo. = 44 mo. 

 44-^-6 = 7 and a remainder of 2. 2 mo. = 60 da. 

 60 da. + 20 da. = 80 da. 8 0-7-6 = 1 3%. The answer 

 is 7 mo. and 13% da. 



Ib. oz. Ib. oz. (avoirdupois) 

 240 12-f-26 12 



This division we may carry out in three" ways, 

 as follows: 



(a) Reduce dividend and divisor to ounces, 

 and divide, as follows : 



Ib. 



240 



oz. Ib. 



oz. 

 12 = 



oz. oz. 

 3852-^-428 = 



(b) Reduce both terms to pounds and di- 

 vide, as follows : 



ib. oz. Ib. 

 240 12-^-26 



Ib. Ib. 



oz. 



12 = 



(c) Divide as the problem reads, as follows: 



9X12 oz. = 108 oz., which equal 6 Ib. and 12 oz. 



9X26 lb. = 234 Ib. 



234 lb. + 6 lb. = 240 Ib. A.H. 



DENT, JOHN CHARLES (1841-1887), a Cana- 

 dian historian whose books are noteworthy for 

 their clear, forceful style and their frank analy- 

 sis of political history. Dent was of English 

 birth, but when still a child was taken to 

 Ontario by his parents, and was educated in 

 the public schools. He was called to the bar 

 in 1865, but spent most of the next ten years 

 in newspaper work, first in London, England, 

 then in Boston, and lastly in Toronto. There- 

 after he devoted himself to historical investi- 

 gation, his chief works being The Canadian 

 Portrait Gallery, a series of biographical 



sketches; The Last Forty Years, a history of 

 Canada between 1841 and 1881; and The 

 Story of the Upper Canada Rebellion. Though 

 occasionally marred by prejudices, these vol- 

 umes in the main are the works of an im- 

 partial, conscientious investigator who stated 

 his honest conclusions, and they marked a 

 great advance in Canadian historical writing. 



DENTISTRY, den'tistri, that branch of 

 medical science which deals with the teeth and 

 surrounding tissues, and their preservation. 

 The progress made in methods and practice 

 of dentistry has been most marked during 

 comparatively-recent years. For ordinary 

 practical purposes dentistry may be divided 

 into two distinct branches, namely, surgical, 

 or operative, and mechanical, or prosthetic. 



Surgical Dentistry. This branch consists in 

 diagnosing the symptoms shown by the 

 patient's mouth and teeth and in giving re- 

 quired treatment. In grandfather's time a 

 dentist was a man who merely extracted 

 teeth. That con- 

 ception has been 

 entirely altered, 

 and extraction is 

 now resorted to 

 only in cases of 

 absolute neces- 

 sity, as for in- 

 stance when THE ADULT TEETH 

 teeth have been (a) Molars; (6) bicuspids; 

 so neglected that < c > canines; (d) incisors, 

 treatment would be of no benefit. Modern 

 dentistry demands the saving treatment of 

 teeth. If teeth are naturally overcrowded or 

 irregularly arranged in the mouth, the dental 

 surgeon will endeavor to overcome those de- 

 fects. If a tooth aches, it is not necessarily 

 an indication that it must be taken out. Care- 

 ful treatment will relieve the ache caused by 

 the cavity in the tooth, and the cavity will 

 be filled. If the decay has exposed the nerve 

 or the pulp of the tooth, the nerve can be re- 

 moved and the root canal filled, making it 

 possible to fill the cavity later. Scaling, or 

 the careful removal of tartar accumulated at 

 the base of the teeth, is another important 

 feature, adding to the life of the teeth. 



Preventive Dentistry in Schools. It was long 

 the notion that the state of a child's first 

 teeth was not important; they must drop out 

 anyway, so why trouble about them? But in 

 recent years there has come increased knowl- 

 edge of the harm which neglected teeth may 

 cause, and as a result preventive dentistry is 



