146 



ANATOMY AND DISEASES OF THE NOSE AND iMOUTH. 



are sn aller, and narrower, and more regular, than the upper ones. They are placed 

 horizcfltally in either jaw; but in the lower the higher side is within, and shelvinj; 

 gradually outward ; in the upper jaw the higher side is without, and shelving inward, 

 and tl us the grinding motion is most advantageously performed. Tliere is also an evi- 

 dent ('ifterence in the appearance and structure of each of the grinders, so that a careful 

 obsei rer could tell to which jaw every one belonged, and what situation it occupied. 



At the completion of the first year, a fourth grinder usually comes up, and the year- 

 ling Eias then, or soon afterwards, six nippers, and four grinders above and below in 

 each jaw, which, with the alteration in the appearance of the nippers that we have 

 Just described, will enable us to calculate nearly the age of the foal, subject to some 

 variations arising from the period of weaning, and the nature of the food. 



At the age of one year and a-half, the mark in the 

 central nippers will be much shorter and fainter ; that 

 in the two other pairs will have undergone an evident 

 change, and all the nippers will be flat. 



At two years this will be more manifest. The ac- 

 companying cut deserves attention, as giving an accu- 

 rate representation of the nippers in the lower jaw of 

 a two-years-old colt. 



About this ]ieriod a fifth grinder will appear, and now, 

 likewise, will commence another process. The first 

 teeth are adapted to the size and wants of the young 

 animal. They are sufficiently large to occupy and fill 

 the colt's jaws; but when these bones have expanded 

 with the increasing growth of the animal, the teeth are separated too far from each 

 other to be useful, and another and larger set is required. Evident provision is made 

 for them, even before the colt foaled. In cavities in the jaw, beneath the first and 

 temporary teeth, are to be seen the rudiments of a second and permanent set. These 

 gradually increase, some with greater rapidity than others, and, pressing upon the 

 roots or fangs of the first teeth, do not, as would be imagined, force out the former 

 ones, but the portion pressed upon gradually disappears. It is ahsorbed — taken up 

 and carried away, by numerous minute vessels, whose office it is to get rid of the 

 worn-out or useless part of the system. This absorption continues to proceed as the 

 second teeth grow and press upwards, until the whole of the fang is gone, and the 

 crown of the tooth, or that part of it which was above the gum, having no longer 

 firm hold, drops out, and the second teeth appear, larger and stronger and permanent. 

 In a few instances, however, the second teeth do not rise immediately under the tem- 

 porary or milk teeth, but somewhat by their side ; and then, instead of this gradual 

 process of absorption and disappearance from the point of the root upwards, the root 

 being compressed sideways, diminishes throughout its whole bulk. The crown of 

 the tooth diminishes with the root, and the whole is pushed out of its place, to the 

 fore part of the first grinder, and remains for a considerable time, under the name of 

 a wolfs hmth, causing swelling and soreness of the gums, and frequently wounding the 

 cheeks. They would be gradually quite absorbed, but the process might be slow 

 and the annoyance would be gnat, and, therefore, they are extracted. 



The change of the teetli commences in those which earliest appeared, and, there- 

 fore, the front or first grinder gives way at the age of two years, and is succeeded by 

 a larger and permanent tooth. 



During the period between the falling out of the central milk nippers, and thb 

 coming up of tlie permanent ones, the colt, having a broken moutli, may find some 

 difficulty in grazing. If he should fall away considerably in condition, he should be 

 fed with mashes and corn, or cut meat. 



The next cut will represent a three-years-old moutli. The central teeth aie larger 

 than the others, with two grooves in the outer convex surface, and the mark 's longf, 

 narrow, deep and black. Not having yet attained their full growth, they arr rather 

 lower than the others. The mark in the two next nippers is nenrly worn out, and it 

 is wearing away in the corner nippers. Is it possible to give this mouth to an early 

 two-years-old 1 The ages of all horses used to be reckoned from May, but some aro 

 frraled even so early as January, and being actually four months over the two years, 



