THE IIOKSE AS A MILLER. 73 



Notwithstanding all these changes it is a rare thing to 

 see a missing incisor or grinder. The canines, how- 

 ever, owing perhaps to their sharp points, not only 

 wear out, but now and then, in extreme old age, fall 

 out. 



The permanent teeth agree with the temporary in 

 but few respects, though the general appearance of the 

 respective teeth is nearly the same. They differ in 

 many respects. Their bodies are larger and denser, 

 and their roots longer and stronger. The grooving of 

 the incisors is the reverse; the outer surface is usually 

 double grooved, the inner smooth, both being slightly 

 rounded. They are less upright in position, and less 

 sharp, but are more discolored, and tlie "marks" (in- 

 fundibula) are wider and deeper and wear out more 

 slowly. They attain their grow^th more slowly, and a 

 healthy tooth continues to grow throughout life. 



In proof of the last assertion many authorities could 

 be cited, but those that follow must suffice. It is a 

 wise provision of Nature, as but for it a horse's teeth, 

 particularly the grinders, would be worn to stubs in 

 two or three years after their development. Prof. 

 M. H. Bouley and Surgeon P. B. Ferguson say (" Vet- 

 erinarian," 1844) : 



"The growth throughout life is a compensation for 

 tlie enormous wear of the teeth, the horse having to 

 perform for himself that which the miller performs for 

 man; and thus during a^^erylong time the teeth pre- 

 serve, if not^ their form, at least their length." 



Prof. A. Chauveau, referring to the horse, says: 



" The permanent teeth present in their development 

 a common but very remarkable characteristic, rarely 

 4 



