DISEASES OF HORSES. 211 



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

 apparent at birth ; there being usually six grinders in each jaw, 

 three on each side in the new born foal, and which number of this 

 set is never increased. The nippers begin to appear soon after 

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

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

 support from herbage as well as milk. The temporaneous set re- 

 ■ciove gradually one after another ; had they all been displaced at 

 he same time, or even had several of them fallen out together, tlie 

 mimal must have suffered great inconvenience, and perhaps have 

 icen starved. This removal, which commences at the age of two 

 ^ears and a half, and is completed between the fourth and fifth 

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

 Appears to be 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 are formed at nearly the same period, and both sets 

 may be thus seen in a dissected jaw. Regulated by the stimulus 

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

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

 evident ; for a premature 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 had 

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

 teeth and jaws must have separated them. 



The forms 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, w^hich, not extending through 

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

 and as a considerable degree of regularity occurs in this wearing 

 away in all horses, it has gradually settled into the generaJ criterion 

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

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

 interval wall or side, which does not become level with the rest until 

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

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

 jaw 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 extremity 

 wears away by age, leaving merely a buttoned process, which may 

 19* 



