746 



THE EXTERIOR OF THE HORSE. 



FIG. 323. Right molar arcades of a very old horse. 

 (The inferior jaw is to the left of the figure.) 



Fig. 323 there are nine. 

 Thus, as we have said ct 

 propos of their structure, 

 when the wear has reached 

 this point there is formed 

 around the dental stumps 

 a thick layer of cement, 

 which, by consolidating 

 them into the alveoli and 

 augmenting the area of the 

 dental tables, permits them 

 still to fulfil their func- 

 tions. 



However, we would 

 make a great mistake 

 were we to believe that 

 these functions are per- 

 formed with the same 

 perfection as when the 

 animal is young. The 

 surfaces of friction, hav- 

 ing lost their bands of 

 enamel, are smooth, round, 

 and deprived of all rough- 

 nesses. Mastication be- 

 comes incomplete, irregu- 

 lar, and the alimentary 

 substances pass through 

 most of the digestive ap- 

 paratus without yielding 

 anything like the sum total 

 of their nutritive princi- 

 ples. Hence nutrition is 

 impaired ; the animal be- 

 comes languid, emaciated, 

 and, little by little, in- 

 capable of working. 



b. Superior Jaw. 

 What we have just now 

 said can, in all respects, be 

 applied to the teeth of the 



