CRIB-BITING. 



559 



Italian war, and took to it again only when he returned to his 

 stable. The same thing happened with respect to cavalry horses 

 which were employed during manoeuvres. Hard work often checks 

 it for the time being, and so does illness, in which case, its renewal 

 may be regarded as a sign of convalescence. 



Fig. 149. — Perpendicular view oi tables of the incisor teeth of a crib- 

 biter (same as Figs. 147 and 148). 



CAUSES. — There is evidently a close connection between the 

 vice of crib-biting and the diminution of work which domesticity 

 entails on the front teeth of stabled horses ; the teeth, being a 

 form of epidermal growth, which is stimulated by pressure (p. 190). 

 In the case of mankind, cooking, by softening the food, is a great 

 cause of dental decay. The human practice of chewing toothpicks, 

 straws, and other comparatively hard substances, is an action 

 obviously prompted by the requirements of dental growth. Horses 



