648 THE EXTERIOR OF THE HORSE. 



CHAPTER III. 



THE CHARACTERS FURNISHED BY THE TEETH. 



At the point at which we have now arrived, is not the reader jus- 

 tified in asking why we have led him into the details of so minute an 

 anatomical description ? Would it not be better, after a summary ex- 

 position of the construction of a tooth, to enter immediately upon what 

 we appropriately call the characters of the age f Evidently not, as he 

 will hereafter comprehend. 



The effects of the friction, pertaining to the dental apparatus, are 

 dow, insensible, and variable, three factors which render the wear diffi- 

 cult of appreciation. Incessantly cleansed, rubbed, polished, worn, 

 and displaced by the action of the saliva, the lips, the cheeks, the 

 tongue, the aliment, and the muscles of mastication, the teeth, which 

 always seem to the eyes of the superficial observer to have the same 

 appearance, nevertheless modify their form at every movement. It is 

 for this reason that M-e have thoroughly studied the configuration, the 

 structure, the mode of eruption, and, in a word, the manner of exist- 

 ence. The wear resulting from these diverse influences is so feeble, 

 when we endeavor to trace it during a short interval, that it necessarily 

 implies, in order to be intelligently recognized, a profound anatomical 

 knowledge. The theoretical details, which have been the theme of the 

 preceding chapters, are consequently justified. 



Restrictions to be made. — Does this mean that we shall neces- 

 sarily obtain invariable indications for the determination of the age ? By 

 no means, for the variety of the conditions of existence of the animal is 

 an influence which the tissues, apparently the most unchangeable, obey 

 like the organism itself. If, for example, the alimentary substances 

 are different in nature, texture, origin, and physico-chemical properties, 

 the functional activity of the tooth will be proportionally increased or 

 diminished, and its resistance to the deteriorating agents will be more 

 considerable or more feeble. Besides, identical results will manifest 

 themselves if the tooth does not possess, in all subjects, the same con- 

 figuration, hardness, inclination, volume, and dimensions. IMoreover, 

 the horses of the North do not mark their teeth like those of the 

 South, East, and West ; those of the mountainous countries like those 

 of the plains ; those of the finer races like those of the common 

 races, etc. As these two sorts of variations, in fact, always exist face 



