VE T ERIN ART DENTAL S URGER 1 '. 75 



cies. The mutability of these agencies are almost 

 infinite, being constantly modified by various exter- 

 nal and internal causes ever present. 



The progress of caries will also be governed some- 

 what by the age of the animal whose teeth it 

 attacks, the nature of the food, as well as the con- 

 stitution of the teeth themselves. The normal con- 

 stituents of the teeth present almost an infinite 

 variety of relative proportions, even in animals of 

 the same age, and continually varying at different 

 ages. As age progresses the teeth like the bones 

 are constantly undergoing a change; the earthy 

 elements increasing and the animal decreasing. 

 This condition arises from defective organizing pow- 

 er or from a failure in the arrangement and com- 

 bination of materials and is entirely dependent upon 

 accidental causes. 



The greater the nutritive supply of a tooth the 

 less liability will there be to caries, hence dimin- 

 ished nutrition increases the liability of caries ; in 

 old animals and especially horses, the teeth receive 

 but little nourishment, so that in them we oftener 

 find decayed teeth than in young animals. 



The decayed portion of the tooth varies in color 

 according to the hardness of the teeth. In some it 

 is black, in others brown, while in some it is nearly 

 white, varying but little from the natural color of 

 the tooth. There are no doubt other circumstances 



