531 



of the incisors rubbed down, the fangs elongated, and those of the upper jaw 

 much curved to bring the crowns in apposition with the procumbent and 

 horizontal incisors of the lower jaw. 



Presented by Bransby S. Cooper, Esq., F.E.S. 



The following is the average course of development and succession of the teeth in the Eqwt* 

 Caballus: The summits of the first functional deciduous molar (d2, 'first grinder' of vete- 

 rinary authors) are usually apparent at birth : the succeeding grinder (d 3) sometimes rises a 

 day or two later, sometimes together with the first. Their appearance is speedily followed by 

 that of the first deciduous incisor (' centre nipper ' of Veterinarians), which usually cuts the 

 gum between the third and sixth days. The second deciduous incisor appears between the 

 twentieth and fortieth days, and about this time the rudimental grinder (pi) comes into place, 

 and the last deciduous molar (d4) begins to cut the gum. About the sixth month the inferior 

 lateral or third incisors, with the deciduous canine, make their appearance. The minute canine 

 is shed about the time that the contiguous incisor is in place, and is not retained beyond the 

 first year. The upper deciduous canine is shed in the course of the second year. The first 

 true molar (m 1) appears between the eleventh and thirteenth months. The second molar 

 follows before the twentieth month. The first functional premolar (p 2) displaces the deci- 

 duous molar (d 2) at from two years to two years and a half old. The first permanent in- 

 cisor protrudes 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 (d3), 

 and the penultimate true molar comes into place. The last premolar displaces the last deci- 

 duous 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 pushes 

 out its deciduous predecessor about the same period. The permanent canine or ' tusk ' next 

 follows : its appearance indicates the age of four years, but it sometimes comes earlier. The 

 third, or outer incisor, pushes out the deciduous incisor about the fifth year, but is seldom in 

 full place before the Horse is five years and a half old. Upon the rising of the third per- 

 manent incisor, or 'corner nipper' of the Veterinarians, the 'colt' becomes a 'horse,' and the 

 'filly' a 'mare,' in the language of the horse-dealers. 



The following specimens illustrate the form and structure of the teeth of the Horse (Eqwu 

 Caballu-i) : 



3158. The dental series of the right side of the upper jaw of a Horse. 



It consists of three incisors, one canine, three premolars, and three true molars. The 

 anterior rudimental premolar has not been preserved. The individual teeth are indicated by 

 their symbols. 



Hunterian. 



3159. The dental series, with the exception of the rudimental premolar, of the right 

 side of the lower jaw of a Horse. Hunterian. 



3 Y2 



