ERUPTION OF THE TEETH. 637 



resistant to wear. Hence the first is always in relief above the second, and the 

 latter above the third. In consideration of this fact, Cuvier rightly said that the 

 molars of the horse were comparable to millstones, which incessantly rub against 

 each other. These asperities of the surface of friction, in fact, render the crush- 

 ing of the alimentary substances much more complete. In old horses, when the 

 enamel bands have disappeared, these substances can without doubt be bruised 

 or broken, but no longer crushed as before. It is for this reason that digestion is 

 less perfect, and that many of the cereal grains, having resisted the actitm of the 

 teeth and the digestive juices, still preserve all their germinating properties after 

 having traversed the entire length of the alimentary canal. 



CHAPTER III. 



ERUPTION OF THE TEETH. 



A. Eruption of the Incisors. 



THE eruption of the milk incisors determines, in general, no par- 

 ticular phenomenon susceptible of attracting the attention of persons 

 who care for the young animal, though it is probable that it sometimes 

 occasions depression and inappetency. For this reason these teeth will 

 not especially concern us here. 



In proportion as the colt approaches the period in which the 

 second dentition begins to appear, certain peculiarities, which it is 

 important to recognize, take place. Thus the head augments in vol- 

 ume and becomes more prominent upon the sides of the region of the 

 face. This aspect of the face is due to the development of the molars, 

 which are enclosed in the alveoli of the superior maxillary bones. 



The effects of this dentition generally seem to pervade the whole 

 organism ; the first attacks of periodic fluxion, strangles, and other 

 diseases manifest themselves at this epoch, as Professor Dupuy and 

 other authors have stated. But if these facts are frequent, it does not 

 follow that they can be extended to the generality of young horses. 



When the colt arrives at the age at which the adult incisors should 

 make their eruption, it is observed that the milk-teeth have already 

 been shed, leaving vacant the place for the permanent teeth, or they 

 may still remain in place. Let us examine the two cases : 



1st. The Milk- Teeth being shed. The spaces which they occupied 

 then present a swelling, tumefaction, and redness, having an ex- 

 aggerated sensibility, which goes so far as to be painful when the 



