8 INTRODUCTION. 



ing through the mouth, as well as causes him to 

 vomit through the nostrils. 



The Teeth. — The manner in which the age of the 

 horse may be determined by an inspection of the 

 teeth will be presently considered ; but there is some- 

 thing in the situation and construction of these parts 

 that deserves notice. The nippers placed in the front 

 of the mouth, in order to cut the grass, are covered 

 with a hard substance called enamel. The enamel 

 passes over the top of the tooth, to be indented and 

 sunk into its centre, forming a pit or hollow. In pro- 

 cess of time, however, this pit or hollow is worn away 

 or ground out ; thus the black marks in the fore teeth, 

 which were nothing but the inside of these hollows, 

 rendered dark by the food getting within them, gra- 

 dually disappear. 



The Tushes. — There is a small space between the 

 nippers and these teeth, as well as between the tushes 

 and the grinders. The tushes are weapons of offence 

 and defence, and very much of the severity of the 

 enraged horse's bite depends upon these teeth. 



The Grinders. — Behind the tushes are the grinders, 

 and they are very curiously constructed. It would 

 not be enough for the food of the horse to be cut and 

 bruised; it must be actually ground down, in order 

 that it may be digested. The back teeth are so formed 

 as to constitute the most perfect grindstones that 

 can be imagined, by means of the roughened surfaces 

 which they present. That these surfaces may not be 

 worn down, or even worn smooth, the enamel is wove 

 in with or twisted about in the substance of the tooth, 

 and is externally covered with a very tough substance 



