49© 



UNGULATES. 



middle finger and toe; the fetlock being the joint at the lower end of the 

 cannon-bone. 



It will thus be evident that the horse is an animal which is supported ex- 

 clusively by a bone in each fore-foot corresponding to the terminal joint of the 

 human middle finger, and in the hind-foot by the representative of the same joint 

 of the middle toe. In this respect the members of this family differ from all 

 other mammals. Indeed, as is well remarked by Sir W. H. Flower, had we not 

 become so thoroughly accustomed to the horse, we should regard it as a very 

 strange and wonderful animal, as in truth it is. 



indications In this place it will be convenient to refer briefly to the changes 



of Age. which take place in the incisor teeth of the horse, with age. As 



already mentioned, the summits of these incisors are characterised by an infolding 



THE UPPER INCISOR AND CANINE TEETH OF THE HORSE AT VARIOUS AGES. 



A at 30 days ; B at 3 years ; C at 6 years ; D at 8 years ; E at 15 years ; F at 30 years. 



of the enamel, deeper in those of the upper than in those of the lower jaw, and 

 common to both the milk and the permanent series. When the teeth are first 

 protruded, as in A of the accompanying figure, the whole of the fold is covered 

 with enamel, but when the teeth are worn (as in C) the edges are cut through, 

 and the centre of the crown is occupied by a pit surrounded with a ring of enamel, 

 this being technically known as the " mark." In the figures, A shows the jaw of a 

 very young colt, with only the first and second milk-incisors protruded, both being 

 unworn ; the third milk-incisor would appear later. In B, which indicates a horse 

 about three years old, the first permanent incisor has just appeared, after pushing 

 out the corresponding milk-tooth. Between three and a half and four years the 

 second permanent incisor would have likewise appeared, and about half a year 

 later the tusk protrudes from the gum. At five years the third incisor would have 

 displaced its predecessor, and the dentition would then be complete. This state is 



