DENTAL INDIOATIOiVS OF THE AGE OF A HORSE. 22.') 



of the bone from the side next the root, and the socket not 

 being sufficiently h^ng, the pressure of the new portion ot 

 the root gives the tooth an outward inclination. Besides, 

 these new portions of the teeth being always narrower, the 

 sockets must necessarily contract, in order to secure the 

 teeth. At this time the sides of the superior maxillaries 

 become flattened, and the head assumes a lengthened and 

 pointed form, which gives to the animal an appearance, which 

 is very indicative of age. The horizontal direction, owing to 

 the same cause, is always a mark of advanced life ; but 

 this direction is much developed in some horses, and not at 

 all in others, the cause of which remains still a question. 



The horizontal direction of the teeth, which increases 

 with the years of a horse, will be easily understood by a 

 reference to plate v. fig. 18. This figure represents the 

 under incisor teeth of a horse known by the name of " Old 

 Billy," which attained his seventy-sixth year, and was per- 

 haps the oldest horse that ever lived. The cranium, with 

 the muscles preserved, is deposited in the Museum of th: 

 ^lanchester Natural History Society, from which I made the 

 drawing. The whole of the incisors are much elongated 

 horizontally, but not perpendicularly elevated more than 

 those of a horse at six years of age. The upper surface of 

 the nippers and dividers are of a quadrangular form, the 

 inner margins being a little rounded ; while the corner 

 teeth are oblong oval, nearly the form of an egg, with the 

 most acute end outwards. The tushes are conical, a little 

 blunted on the crown, and turned backward, with an 

 elongated, shallow, curved groove on their inner sides. I 

 will be seen that the outer edge of all the cutting teeth is 

 nearly parallel, the corner teeth being only a little less pro- 

 duced than the others. It does not appear that the jaw- 

 bones themselves have been lengthened, the teeth alone 



2g 



