DIFFERENT KINDS 0F| TEETH. 751 



preceded by milk teeth, and are consequently permanent. Very 

 small, pointed teeth are frequently found in the mouths of foals 

 where the canines subsequently appear. Some authorities regard 

 these minute teeth as rudimentary milk tushes; but they are so 

 insignificant in size that, practically speaking, even while con- 

 ceding this point, the canines may be looked upon as permanent 

 teeth. 



The typical dental formula of the mammalia (animals which 

 suckle their yoimg) is (taking one side of each jaw) : — 



3 1 4 3 



incisors — canines — premolars — molars — ^ 44. 

 3 1 4 3 



The teeth of the ancestors of the horse, from the pliohippus 

 upwards, conformed to this arrangement; but the horse of the 

 present day has, as a rule, only 3 premolars (2nd, 3rd, and ith) ; 

 although in embryo, the 1st premolar is always present. It is 

 occasionally found in the upper jaw (Figs. 229, p. 781 and 241, 

 p. 790), seldom in the lower jaw, and very rarely in both jaws. 

 These teeth, popularly called " wolf's teeth," are of comparatively 

 small size and have only one root. They are said always to be 

 found in the upper jaw, usually appear at the age of 5 or 6 

 months ; generally fall out along with the second milk premolar, 

 at about the age of 2 J years ; and are not replaced. They some- 

 times remain permanently in the jaw. They are vestigial, and not 

 supernumerary . teeth. 



The two front incisors are termed central incisws ; the next 

 pair, lateral incisors; and the two farthest back, corner incisors. 

 The premolars and molars are numbered respectively, 1, 2, 3, 4, 

 and 1, 2, 3, from the front backwards. 



Omitting the first premolar on account of its insignificant size 

 and inconstant appearance, we may state that a horse with a 

 " full mouth " has 40 permanent teeth, namely, 12 incisors (6 in 

 each jaw), 4 canines, and 24 back teeth (6 premolars and 6 

 molars in each jaw) ; and a mare with a " full mouth " has 36 

 teeth. Consequently, their respective permanent dental formulae 



3 1 3 3 3 3 3 



i — e — pm — m — = 40, and i — pm — m — =36. 



3 13 3 3 3 3 



The milk dental formula of both horses and mares is : — 



3 3 



i ^ pm — "=• 24. 



3 3 



