CAUSE OF THE YELLOW COLOB. 207 



"At sixteen the dividers are triangular, and the cor- 

 ner teeth are becoming so. 



" At seventeen the corner teeth, like the dividers and 

 centrals, have become triangular, the sides of the tri- 

 angles being equal. 



"At eighteen the lateral portions of the triangles 

 lengthen in succession first in the centrals, next in 

 the dividers, and then in the corners; so that at nine- 

 teen the lower centrals are flattened from one side to 

 the other; at twenty the dividers are flattened, and at 

 twenty-one the corners also are." 



The three following extracts give some idea of the 

 difficulties to be encountered in judging the age by 

 the teeth. Prof. Youatt says: 



"Stabled horses have the marks sooner worn out 

 than those at grass, and a ' crib-biter' may deceive the 

 best judge by one or two years. At eleven or twelve 

 the lower nippers change their original upright posi- 

 tion and project forward. They become of a yellow 

 color, the cause of which is that the teeth grow to 

 offset their wear ; but the enamel which covered their 

 surface when they were young cannot be repaired, and 

 that which wears this yellow color in old age is the 

 part which was formerly in the sockets. The gums 

 recede and waste away, and the tushes wear to stumps 

 and project outward." 



Surgeon Ewd. Mayhew says ("The Horse's Mouth: 

 Showing the Age by the Teeth") : 



"That the teeth of the horse denote age appears to 

 have been a very ancient belief, which the experience 

 of centuries has not changed. Within certain limits 



