TEETH OF OTGULATA. 



85.5 



place. The upper deciduous canine is shed in the course of the 

 second year. The rise to working level of the third deciduous in- 

 cisors or ' corner nippers ' completes the stage of dentition called the 

 ' colt's mouth ' by veterinary authors, fig. 282. The deciduous inci- 

 sors are not only smaller than the permanent ones, but are whiter, 

 have a better marked ' neck,' the fang more slender and pointed, and 

 are devoid of the median longitudinal groove. The first permanent 



283 284 



Incisive dentition of 3-year <>kl Cult. 

 Lower jaw. 



IncNive dentitinji of 4-year old Colt. 

 Lower ja\v. 



molar, m i, appears between the eleventh and fourteenth months. 

 The f second ' molar, m 2, follows at the twentieth month or the 

 second year. The first functional premolar, p 2, displaces the deci- 

 duous molar, d 2, at from two years to two years and a half old. 1 

 The first permanent incisor, fig. 283, i i, displaces d 3, and pro- 

 trudes from the gum at between two years and a half and three 

 years. At the same period the second or penultimate premolar, p 3, 

 pushes out the penultimate milk-molar,, and the penultimate true 

 molar, m 2, comes into place. The last premolar, p 4, displaces the 

 last deciduous molar at between three years and a half and four 

 years; the appearance above the gum of the last true molar, m 3, is 

 usually somewhat earlier. The second incisor, fig. 284, i 2, pushes 

 out its deciduous predecessor at about three years and eight months. 

 The permanent canine or ' tusk,' c, next follows ; its appearance 

 indicates the age of four years and a half; but it sometimes comes 

 earlier. The third, or outer incisor, fig. 285, i 3, pushes out the de- 

 ciduous incisor, d 3, about the fifth year, but is seldom in full place 

 before the horse is five years and a half old ; the last premolar is 

 then usually on a level with the other grinders. Upon the rising 



1 The homologous teeth in the young Hyrax, fig. 287, are indicated by the same 

 symbols, and the sole developmental difference from the Horse is the displacement r-\ 

 d ] by up 1 of functional size. 



A A 2 



