20 



ANIMAL DlCXTIS'lkV. 



aiid encrusted over the rcmainiiif^ portion witli crusta pe- 

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

 occupies a cavity within the 1)ody of the tooth, the aveolo- 

 dental periosteum which surrounds tlie external surface of 

 the fano-, the .churns or gingivae, which cover the neck, the 

 blood vessels which supply its nutrition, and the nerves 

 whicli furnish its sensil)ility and tactile sense. 



DENTINE. 

 The dentine is a hard, yel]o\\-ish, sensitive substance con- 







"f'j 



mm,'/ 



'iHiriilh'l iM„lllul!.illlUI|ht|!,;l||((||K|||| 



Fig. ta. 



Enamel and Dentine as .Arranged at 

 the Crown. 



1. F.naniel. 



2. Spaces of Czcrmak. 



3. T'cntiiK?. 



(Magnified.) 



Fig. 2. 

 Dentinal Tnlndes. Ma'Jjnified. 



stitutino- the major ])ortion of the tooth's volume. It ex- 

 tends from the j)ulp cavity within to the enamel and crusta 

 petrosa without. Chcnu'cally it shows the followiu"- compo- 

 sition : 



Carbonate of lime 7-97 



Phosphate of lime ^^'7-54 



Phosphate of magnesia 2.49 



Fluoride of lime a trace 



