78 VETERINAIiY STATE BOARD 



Give the permanent dental formula of (a) the horse, (b) the ox, (c) 

 the dog. 



(a) " 



(b) 



(c) 



Describe an incisor tooth. 



Pyramidal, flattened from before, backward, with a single fang. 

 Three surfaces, anterior, indented by a slight longitudinal furrow, 

 which is prolonged to the root ; a posterior face, rounded from side 

 to side and concave from above downward, and two borders, of which 

 the internal is always thicker than the external ; last, a surface of 

 friction, the table. 



In composition, there are three fundamental substances: the 

 dentin envelops the pulp cavity, the enamel covers the dentin. The 

 enamel is doubled in the external dental cavity, lining it throughout, 

 and when the surface of friction is in wear, a ring of enamel sur- 

 rounds that surface and an internal ring of the same surrounds the 

 infundibulum. The first circle forms what is called the encircling 

 enamel ; the second, the central enamel. Over the enamel is a pro- 

 tecting substance, the cementum or crusta petrosa, which disappears 

 soon after the tooth becomes in wear. 



Give the general arrangement of dentin, enamel and cementum from 

 without, inward, in the following teeth: (a) incisor, (b) 

 canine, (c) molar. 



(a) Cementum, enamel and dentin. 



(b) Cement, enamel and dentin. 



(c) External cement, external enamel, dentin, internal enamel 

 and internal cement. 



State the difference between the incisors of the horse and those of 

 the ox. 



(See description of horse's incisor above.) 



In the ox, the incisors are eight in number, all in the lower jaw. ~ 

 They are not fixed in the alveoli, as in ttfe horse, but have a certain 

 degree of mobility. The root is more conical in shape, giving the 

 tooth a shovel-like appearance, the root being the handle. On the 

 middle of the internal face, is a conical eminence, the base of which 

 widens and terminates near the free extremity of the tooth. As 

 age and wear advance, the teeth seem to separate from one another, 

 and in youth they only touch by their extremities. 



