HORSE. 



581 



caducis,' &c.(l) Bojanus never found the lower deciduous canine 

 retained beyond the first year. The deciduous canine of the upper 

 jaw, being developed at a short distance behind the incisors, in 

 the maxillary bone, is less disturbed by the eruption of the outer 

 incisor, but is neverthess shed in the course of the second year. 

 The deciduous canines appear from Camper's observations, to retain 

 their place longer in the Zebra than in the Horse. (2) 



M. Rousseau, who describes the first dentition as being terminated 

 by the appearance of the lateral incisors, assigns from the seventh to the 

 tenth month as the period of its completion. (3) The deciduous in- 

 cisors have thinner and more trenchant, normally-shaped crowns than 

 those of their permanent successors. The first true permanent molar 

 (fig. 5, m 1) appears between the eleventh and thirteenth months. 

 The second true molar (ib. m 2) follows between the fourteenth 

 and twentieth month. The crowns of the premolars and the last 

 true molar are now advancing in the closed sockets of reserve, 

 as shown in PI. 136, fig. 5. The first premolar {p 2) (essentially 

 answering, as in the Ruminants, to the second of the Anoplothere) , 

 displaces the second {d 2) and, usually at the same time, the first very 

 small deciduous molar, at from two years to two years and a half 

 old. The first permanent incisor (fig. 6, i \) rises above the gum 

 between two years and a half and three years. At the same period 

 the second premolar (ib. & fig. 5, p. 3) pushes out the third deci- 

 duous molar {d 3). The last premolar (ib. p. 4) displaces the last 

 deciduous molar (ib. d 4) about the completion of the fourth year, 

 and the appearance above the gum of the last true molar (ib. m 3) 

 is usually anterior to this. Figure 6 shows the state of the den- 

 tition about this period, and should the last deciduous molar {d 4) 

 have been prematurely drawn, the position of the crown of its 



(1) Nova Acta Nat. Cur., torn, xii, pt. ii, 1825. p. 697. The tooth which M. Rousseau 

 figures in his ' Anatomie Comparee du Systeme Dentaire,' PL xxv, fig. 2, as the "crochet 

 caduc de lait," in a Horse about three years old, appears rather to be the small canine of a 

 Mare. Compare with fig. 8, PI. 26, of the same work, where no trace of the * crochets caducs,' 

 appears in a Horse of two years old. 



(2) CEuvres de Pierre Camper, Paris, 1805. 



(3) The appearance of the third deciduous incisors, or * corner nippers', completes the 

 stage of dentition Ccdled the 'colt's mouth' by Veterinary Authors. 



