THE TISSUES. 



1. The solid, homogeneous intertubular substance. 



2. The dentinal tubuli. 



A. The intertubular substance is perfectly structureless, and con- 

 sists in great part of the phosphate of lime in combination with an 



Fig. 230. 





^'&Q::m 



.':^-A : 'V^'^ '.:' ' 



X v 



Fig. 230. Vertical section of human incisor, showing the general arrangement of its constituent 

 parts. The dentine, the pulp-cavity, the enamel on the body, and the bone or cementum on the fang, 

 are seen. a. Neck of the tooth. (Magnified 3 diameters.) 



Fig. 231. Transverse sections of tubules of dentine, showing their cavities, their walls, and the 

 intertubular tissue, a. Ordinary distance apart, b. More crowded, c. Another view. Human 

 molar. (Magnified 400 diameters.) 



organic substance, doubtless osteine. 1 According to Mr. Tomes, it 

 is made up of minute granules closely united; and these pass into 

 his " granular layer" between the dentine and the enamel. (Fig. 

 232, d.) 



Chemical analysis of the solid substance of dentine gives the fol- 

 lowing results. There is more mineral matter in the molar than in 

 the incisor teeth. 



Phosphate of Lime 64 j- 



Carbonate of Lime 5J 



Phosphate of Magnesia and Soda, and Common Salt 2 J 



Organic Substance (Osteine) 28 



100. 



1 For it affords glutin on boiling. 



