DENTAL INDICATIONS OF THE AGE OF A HORSE. 225 
of the bone from the side next the root, and the socket not 
being sufficiently long, the pressure of the new portion oi 
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 the 
Manchester 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 i3 
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 
