20 



ANIMAL DENTISTRY. 



and encrusted over the remaining portion with crusta pe- 

 trosa, or cement. The soft structures are the pulp, which 

 occupies a cavity within the body of the tooth, the aveolo- 

 dental periosteum which surrounds the external surface of 

 the fang, the gums or gingivae, which cover the neck, the 

 blood vessels which supply its nutrition, and the nerves 

 which furnish its sensibility and tactile sense. 



DENTINE. 



The dentine is a hard, yellowish, sensitive substance con- 



FlG. I A. 



Enamel and Dentine as Arranged at 

 the Crown. 



1. Enamel. 



2. Spaces of Czermak. 



3. Dentine. 



(Magnified.) 



Fig. 2. 

 Dentinal Tubules, Magnified. 



stituting the major portion of the tooth's volume. It ex- 

 tends from the pulp cavity within to the enamel and crusta 

 petrosa without. Chemically it shows the following compo- 

 sition : 



Carbonate of lime \ . 7.97 



Phosphate of lime ^7-54 



Phosphate of magnesia 2.49 



Fluoride of lime a trace 



