174 ELEMENTS OF HISTOLOGY. [Chap. xxi. 



tubes pass into a layer of intercommunicating irregular 

 branched spaces, the interglobular spaces of Czermak, 

 or the granular layer of Purkinje. These communicate 

 with spaces existing between the bundles of enamel 

 prisms of the crown, as well as with the bone lamina 

 of the crusta petrosa of the fang. The interglobular 

 spaces contain each a branched nucleated cell. The 

 dentinal fibres anastomose with the processes of these 

 cells. The incremental lines of Salter are lines more 

 or less parallel to the surface, owing to imperfectly cal- 

 cified dentine the interglobular substance of Czermak. 

 The lines of Schreger are curved lines parallel to the 

 surface, and due to the optical effect of simultaneous 

 curvatures of dentinal fibres. 



230. The cement is osseous substance, being 

 lamellated bone matrix with bone corpuscles. There 

 are no Haversian canals. 



231. The pulp is richly supplied with blood-vessels, 

 forming networks, and extending chiefly in a direction 

 parallel to the long axis of the tooth. Numerous 

 medullated nerve-fibres forming plexuses are met 

 with in the pulp tissue ; on the outer surface of the 

 pulp they become non-medullated fibres, and probably 

 ascend in the dentinal tubes. The matrix of the 

 pulp is formed by a transparent network of richly 

 branched cells, similar to the network of cells forming 

 the matrix of gelatinous connective tissue. 



232. On the outer surface of the pulp i.e., the 

 one in contact with the inner surface of the dentine 

 is a layer of nucleated cells, which are elongated, 

 more or less columnar. These are the odontoblasts 

 proper. Between them are wedged in more or less 

 spindle-shaped nucleated cells, the outer or distal pro- 

 cess of which passes into a dentinal fibre. The odonto- 

 blasts proper are concerned in the production of the 

 dentinal matrix, according to some by a continuous 

 growth of the distal or outer part of the cell and 



