COHTltfUOUS WEAR AND GROWTH. 305 



course to in caries. In our subjects it is best to remove all decayed 

 portions. In removing the decomposed dentine such instruments 

 should be selected as would seem best adapted to the purpose, We 

 must not forget that the cavity must be so formed as to retain the 

 filling when properly introduced. To do this it is most always nec- 

 essary to remove more or less solid dentine to secure suitable re- 

 taining points. " In large cavities where one side of the tooth is 

 weak, places must be selected for making retaining points that will 

 least affect the weak point." (Taft.) There are several ways of 

 forming retaining points. Under-cutting and grooving is practiced 

 by some; others prefer to drill little holes or pits into the dentine, 

 these taking effect in different directions. In the molars we can 

 leave the cavity larger at the bottom than at the orifice, dove-tailing 

 it as it were. In cutting the direction should be from the nearest 

 point of pulp exposure toward the orifice of the cavity. After the 

 cavity is formed, and before introducing the filling, it must be 

 thoroughly dried with bibulous paper and the warm-air blow-pipe. 

 In preparing amalgam for filling, put a sufficient quantity in a mor- 

 tar, add mercury sufficient to give the requisite plasticity, and then 

 wash thoroughly to remove the oxide. The excess of mercury can 

 be removed by pressing the paste in a piece of chamois or between 

 the thumb and finger. Then break into small pieces and press each 

 piece firmly into the cavity till it is full. Burnish with the corun- 

 dum point till smooth and bright. 



Dr. Sayre, who is a lecturer in the Chicago Veterinary College, 

 studied human dentistry before either practicing or teaching veter- 

 inary dentistry. All veterinary colleges should have a Sayre. 



THE CONTINUOUS GROWTH OF HORSES' TEETH. 



MOST veterinarians are agreed that the wear of horses' teeth is 

 offset by growth (growth after full development), but they differ as 

 to how long this process continues. But it is plain that the growth 

 is equal to the wear just as long as the teeth maintain their natural 

 length. Wear will depend somewhat on the kind of food a horse is 

 fed on, but both the growth and the wear will differ in individual 

 horses, no matter how healthy or well fed they may be. Contin- 

 uous growth will depend not only on the health of the animal and 

 the food it eats, but on the health of the teeth themselves. These 

 three factors are indispensable to an intelligent determination of the 

 question of continuous growth. 



Continuous growth is well illustrated on page 73 of this work. 



