54 



ANATOMY AND PHYSIOLOGY OP 



markable period) in the age of the horse ; 

 have briefly considered a series of changes 

 which the teeth of a colt undergo, up to 

 the period of maturity, and shall now turn 

 our attention to the changes observed in 

 the process of wear and tear of the perma- 

 nent teeth. 



REMARKS ON THE CHANGES 

 WHICH A HORSE'S TEETH 

 UNDERGO. 



The nippers or front teeth of a full- 

 mouthed horse, just having shed all the 

 temporary ones, present a beautiful ap- 

 pearance : the contrast between the lily 

 whiteness of the teeth, and the rose-tinted 

 color of the gums and their membranes, are 

 never so much the subject of admiration as 

 at this period. 



Teeth, when first cut, present a sharp 

 border externally, from which a gi'adual 

 depression commences until the internal 

 border is reached ; in the course of about 

 a year, in consequence of friction on the 

 external, and growth of the internal, the 

 surface presents two elliptical enamelled 

 rims, one of which borders the face of the 

 tooth, the other encircles the depression or 

 pit. 



Within this pit is a black incrustation, 

 which is denominated "bean " or " mark ; " 

 at a period of about three years from the 

 time of cutting the permanent teeth, the pit 

 or cavity is consolidated or filled up, and 

 the surface of the tooth is worn down so as 

 to present a comparatively smooth one. 

 We must not expect, however, to find the 

 face of the teeth uniform ; for cribbers, and 

 voracious feeders, deface the surfaces very 

 much, which gives to the teeth the appear- 

 ance of age. Still, a good judge, who takes 

 into consideration not only the appearances 

 of surfaces, but also the form and direction 

 of the teeth themselves, is not apt to be 

 deceived regarding the age of a full-mouthed 

 horse. 



Pessina, from whose work Mr. Percivall 

 quotes, concludes that — 



" At the age of eight (in most horses). 



the disappearance of the marks is perfect: 

 the teeth are all oval, the central enamel 

 upon the face is triangular, and nearer to 

 the outward than the inward border, and 

 the cavity of the tooth appears within tlie 

 outward border like a yellowish band canied 

 from one side to the other. 



" At nine years, the front teeth appear 

 round, the middle and the lateral contract 

 their oval faces, and the central enamel di- 

 minishes and approaches the inward border. 



" At ten, the middle teeth become round, 

 and the central enamel has approximated 

 the inward border and is rounded. 



" At eleven, the middle teeth are rounded, 

 and the central enamel is almost worn off 

 the posterior incisors. 



" At twelve, the lateral teeth are rounded, 

 the central enamel has quite disappeared : 

 the yellow band has grown wider, occupies 

 the centre of the face of the tooth, and 

 the central enamel continues in the teeth 

 of the upper jaw. 



" At thirteen, all the incisors are rounded, 

 the sides of the front teeth spread out, and 

 the central enamel continues in the upper 

 jaw, but is round and approaches the inward 

 border. 



" At fourteen, the faces of the front inci- 

 sors put on a triangular appearance, the 

 middle grow out at their sides, and the cen- 

 tral enamel of the upper teeth diminishes, 

 but still exists. 



" At fifteen, the front teeth have become 

 triangular, the middle enter upon that 

 figure, and the central enamel of the upper 

 jaw is still visible. 



" At sixteen, the middle are triangular, 

 the lateral commence that shape, and the 

 enamel of the upper teeth has disappeared. 



" At seventeen the triangular figures of 

 the posterior jaw are completed ; but their 

 triangles are equilateral until the eighteenth 

 year. Then their sides lengthen in succes- 

 sion from the front to the lateral teeth, in 

 such a manner that — 



" At nineteen, the front teeth are flat- 

 tened from side to side ; 



" At twenty, the middle incisors have 

 taken on the same shape ; lastly — 



