MASTICATION. 255 



TO DETEKMINE THE AGE OF THE DOMESTIC ANIMALS BY THE TEETH.* 



It is chiefly by the incisor teeth that we can tell how old a horse 

 is, and it is important to consider the change in shape and general 

 appearance which these teeth undergo. There are temporary and per- 

 manent incisors. The first have a broad crown, flattened somewhat 

 from before back, with a wearing surface far wider from side to side 

 than from behind forward. They have a distinct neck, and a narrow, 

 sharp fang. The appearance of the temporary teeth is shelly, and there 

 is a well-marked depression or infunclibulnm on the upper aspect. The 

 front of the tooth is of a pearly white, and is grooved or fluted. The 

 permanent incisor is much larger than the temporary, tooth ; its crown 

 thicker, of a duller color, and the cavity or infundibulum is deeper. The 

 neck of the tooth is not so well defined, and as the animal acquires age 

 we find a veiy remarkable change in the shape. This is seen in Fig. 101 , B, 

 which represents different sections of the permanent incisor, as its surface 

 appears from progressive wear. It is from birth to the age of eight 

 years that from the condition of the " marks" or dark cavities in the 

 table of the incisors we can determine the age of the horse. There are, 

 however, deceptive cases. 



The molar teeth are rarely looked at in determining the age of the 

 horse, but they furnish valuable corroborative evidence, especially in 

 young animals. They are not easily examined, but it is their number 

 which in the colt confirms or negatives the opinion expressed as to the 

 animal's age. The recently-formed molar has a shelly character (Fig. 

 101 , C) and prominent tubercles of enamel, which soon wear down to form 

 a broacl, grinding surface, and then the young and old teeth are not 

 easily distinguished. 



The horse has six incisors above and six below. The} 7 are compound 

 teeth, as shown in Fig. 101 at A, and the cavity extends downward, 

 having beyond and a little in front of it the pulp-cavity, which in old 

 horses as the teeth wear down is indicated by a dark, hard structure, 

 which then fills it, and which is called osteodentine. 



The temporary incisors are in perfect apposition as the colt 

 approaches two years, and not seldom an animal, especially a pony, has 

 been bought for five years of age from the temporary teeth being mis- 

 taken for the permanent incisors. The temporal incisor is gradually 

 displaced by pressure from the permanent. The latter advances, and has 

 a shelly aspect, seen in a, Fig. 101, at B. At 6 the incisor tooth indicates 

 two years' wear; at c five years', at d nine years', and at e about 



*This chapter is taken from Gamgee, "Our Domestic Animals in Health and in 

 Disease." 



