192 



MAMMALIA. 



years and a half to four years the intermediate fore-teeth expe- 

 rience the same change, and the lower tushes begin to make their 

 appearance. The corner-teeth are also renewed when between four 

 and a half to five years; the upper tushes likewise pierce the gums, 

 and about the same date the sixth grinder shows itself. 



A depression, or small hollow, may be noticed on the surface of 

 the crown of the second growth of fore-teeth, just as in the milk- 

 teeth, and these hollows are gradually worn away in the same 

 fashion. 



The^rMjecrs of the lower jaw lose their cavities when the Horse 

 is five or six years old ; the intermediate fore-teeth are the next 

 to raze. The marks in the corner-teeth are obliterated at the age 

 of seven or eight years. The process of destruction of the marks 

 in the upper fore-teeth goes on in the same order, but more tardily. 

 (Figs. 51 and 52). 



FiR. .50.— Six j-p 



Fig. 51. — Nine years. 



When all these various changes have taken place, the Horse is 

 looked upon as aged (Fig. 53), because the teeth no longer furnish, 

 any certain indications as to the age of the animal. Only 

 approximate inferences can now be drawn from the length and 

 colour of the tusks, which become more and more bare and 

 projecting from the gum, &c. 



The domestication of the Horse appears to date back to the very 

 earliest period of his appearance on earth ; and as this animal 

 adapts itself to every necessity, every want, and every climate, 

 its subjection has resulted in a considerable number of races, 

 distinguished by more or less prominent characteristics of shape, 

 strength, temper, and endurance. Although generally intelli- 

 gent, affectionate, and endowed with considerable powers of 



