DISEASES OF HORSES. 211 



Di ites participate.. The miik set are some of them, as the molars, 

 a|>j»arent at birth ; there being usually six grinders in each jaw, 

 thi e on each side in the new born foal, and which number of thijj 

 set II, never increased. The nippers begin to appear soon after 

 birtk, and follow a regular order of succession, until the animal is 

 three -or four months old ; at which time he begins to require 

 suppot-t from herbage as well as milk. The temporaneous set re- 

 tiove g.ddually one after another ; had they all been displaced at 

 •lie sam*. time, or even had several of them fallen out together, the 

 mimai rririst have suffered great inconvenience, and perhaps have 

 jeen starv«»d. This removal, which commences at the age of two 

 /ears and « half, and is completed between the fourth and fifth 

 /ear, is effected by the action of the absorbents on their fangs, and 

 Appears to W occasioned by the. stimulus of the pressure received 

 from the growing teeth under them. For although these two sets 

 appear with an interval of some years between them ; yet the rudi- 

 ments of both -«re formed at nearly the same period, and both seta 

 may be thus st.*n in a dissected jaw. Regulated by the stimiilus 

 of necessity, a^ soon as the temporaneous set falls out, the perma- 

 nent appears : und that such appearance follows the necessity, is 

 evident ; for a preinature or accidental removal of the colts' teeth 

 is soon followed by the appearance of the others. Dealers and 

 breeders aware of this, draw the milk teeth to make their colts 

 appear as horses. It was necessary there should be two sets of 

 teeth, for as they grow slowly in proportion to the jaws, so haa 

 there been but one only, the disproportion of growth between tho 

 teeth and jaws must have separated thein. 



The forvis of the teeth vary more than their structure. The inci 

 sive or nippers- are round, which is favourable for the pressure they 

 undergo ; the upper more so than the lower. On the upper surface 

 a hollow is seen in the young tooth, which, not extending through 

 the whole substance, naturally wears out with the wear of the tooth ; 

 md as a considerable degree of regularity occurs in this wearing 

 4 ivay in all horses, it has gradually settled into the general criterion 

 >f age. The nippers are not all of them exactly similar ; the corner 

 eeth differ most in being exactly triangular, and in having an 

 nterval wall or side, which does not become level with the rest uniil 

 .ong after the others. The cuspidate tusks or tushes are permanent, 

 appearing at about five years, or rather earlier ; those in the front 

 faw are usually nearer the nippers than those below. Each pre- 

 sents a slight curve, which follows the direction of all the canine 

 or pugnatory teeth of other mammalia. The pointed extremit;y 

 wears away by age, leaving merely a buttoned piocess, which ma> 

 19* 



