DENTAL INDICATIONS OF AGE OF A HORSE 1 87 



DENTAL INDICATIONS OF THE AGE OF A 



HORSE. 



Nothing can more clearly indicate a proof of 

 design than the beautiful contrivance in the forma- 

 tion of the molars of the horse for the purposes 

 required. They are, like the incisor teeth, covered 

 on the sides with enamel, but not on the top, 

 though several portions of enamel enter into their 

 substance in their internal structure. They are 

 subjected to much more friction than the cutting 

 teeth in grinding down the harder portions of then- 

 food, and nature has made ample provision for their 

 strength and endurance. 



We have given a representation of the section 

 of a grinder (Plate v, fig. 12) to show its Interior 

 structure. The teeth are prepared and formed in 

 cavities within the jaw-bones. In the unborn 

 animal a delicate membranous bag, containing a 

 jelly-like substance, is situate in the small cell 

 within the javv^-bone. By degrees this substance 

 assumes the form of a tooth, and then the 

 jelly within the membrane begins to change to a 

 bony consistence ; then a hard crystallisation is 

 formed on the outside of this membranous cover- 

 ing. This is the enamel of the tooth. In the 

 formation of each grinder of the horse in the upper 

 jaw, there are originally five of these membranous 

 bags filled with jelly, and four in the lower jaw. 

 This jelly is gradually superseded by bony matter, 

 which is deposited by little vessels penetrating into 

 it. These vessels are represented by the black 

 streaks in the carker central portions of the figure, 

 around each of which the crystallisation of enamel 

 can be distinctly traced, so that there would be five 



