104 



MANUAL OF HISTOLOGY. 



numerous passages having, like the enamel prisms, a direction 

 at right angles to the surface of the bone. These passages, the 

 dentinal canals, are united with one another laterally by 

 minute oblique branches, and form undoubtedly open channels 

 of communication between the pulp cavity and the spaces be- 

 tween the enamel prisms in the crown and the bone lacunae of 



the cement in the fang. Each canal 

 -^=^^^E^^^ is lined with a particularly delicate 

 and resistant membrane, the den- 

 tinal sheath of Neumann. 



Upon the internal surface of the 

 dentine, or the external surface of 

 the pulp- tissue, is the layer of 

 odontoblasts (Schwann). These cor- 

 puscles, according to Waldeyer, 

 have long branching processes ex- 

 tending in three directions, inward 

 into the pulp-cavity, outward 

 through the dentinal channels, 

 forming the dentinal fibres of 

 Tomes, and laterally so as to form 

 connection with adjacent corpus- 

 cles. On the outer surface of the 

 dentine the canals connect with 

 the interglobular spaces of Czer- 

 mak, and they in turn are con- 

 tinuous with interstices between 

 the enamel prisms. The dentinal 

 tubules never appear to be in di- 

 rect communication with the enam- 

 el spaces, but only mediately, as 

 has been described. These cavi- 

 ties are filled with protoplasmic 

 material. Those immediately adjoining the cement are small 

 in size, and form what is known as the granular layer of 

 Tomes or PurJcinje. 



Dentinal globules (Fig. 39, 2) is the name given to certain 

 spheroidal masses that are regarded (Waldeyer) as calcified 

 remains of the corpuscles in the spaces. The contours of these 

 masses correspond in outline with those of the interglobular 

 spaces. 



FIG. 39. Canine tooth of man, present- 

 ing a portion of the transverse section of 

 the root : 1. cement with larsre lacunae and 

 parallel striae ; 2, interglobular substance ; 

 8, dentinal tubulea. Magnified 300 diame- 

 ters. (Waldeyer.) 



