LECTURE VII 



THE DENTITION OF HORSES, CATTLE, SHEEP, 

 PIGS, AND DOGS, AND DENTAL DISEASES 



342. Teeth are the principal agents in mastication, and, although 

 composed of the hardest structures in the body, are, in the 

 first instance, developed by a very interesting process from one 

 of the softest structures — the mucous or lining membrane of the 

 mouth. 



343. The Tooth is divided into the crown, neck, and root, and 



is made up of three structures — ivory, or dentine ; enamel ; and cement, 

 or cvusta petrosa. The dentine is whitish-yellow in colour, and 

 forms the bulk of the tooth. It is found in the middle, in contact 

 with the pulp, and consists of about 72 per cent, earthy matter and 

 about 28 per cent, animal matter. The enamel — the hardest sub- 

 stance of the three — is of a pale bluish-white, and contains 95 per 

 cent, earthy and 5 per cent, animal matter. It acts as a protection 

 covering the external parts of the crown, and is interspaced in irre- 

 gular curves between the dentine and cvusta petrosa. The crusta 

 petrosa is yellowish-white, and found on the outside of the tooth, 

 in connexion with the root, or fang, and is softer than either the 

 dentine or enamel ; in fact, it is the bone of the tooth, and is com- 

 posed of 67 per cent, earthy and 33 per cent, animal matter. 



344. There are two sets of teeth — viz., Temporary, or Milk 



Teeth, which are much smaller and whiter than the second set, the 



Permanent (see par. 348). 



230 



