610 



THE EXTERIOR OF THE HORSE. 



turbed in its cavity of reception, and so much the more as the surface of friction 

 is less extensive, for the animal is obliged to increase the frequency of the move- 

 ments to compensate for the imperfections of its instruments of mastication. 



Fig. 284.— Radical cementation of the incisors of tlie horse. 

 A. Dental tables. I B. View of the same teeth in their alveoli. 



These continual displacements to which the dental stumps are submitted 

 stimulate the action of the alveolar periosteum, whose irritation is manifested 

 by the production of very dense osseous layers which are deposited in propor- 

 tion to the intensity of the dental displacements, and solidly seal the tooth in its 

 alveolus at the same time that they increase the area of its surface of friction. 



It is perceived that this cementation is the more active as the dental stump 

 is shorter, narrower, and the aliment coarser ; in a word, as it offers less resist- 

 ance to the diverse causes tending to break its adherence with the living parts. 

 Thus, in the horse, it is the teeth of the inferior jaw, those which occupy the 

 centre of the incisor and molar arcades, which present the greatest thickness 

 of radical cement. The violent and brutal tractions exercised upon the bit often 

 lead to similar formations around the corner teeth. The same results are 

 observed, finally, after surgical operations in which a tooth is accidentally dis- 

 turbed or partially dislocated in its alveolar cavity. 



It is easy to comprehend the utility, to the organism, of such a new forma- 

 tion. The nature of the aliment on which our large herbivora subsist would 



