628 THE TEETH. 



parallel rows, and extend a considerable distance without forming a net-work. 

 The dentine and cement are connected together by means of a layer composed 

 of an agglomeration of transparent globules, of varying degrees of thick- 

 ness. The spaces intervening between the latter (interglobular spaces) 

 are irregularly notched, and frequently in very close proximity to one 

 another ; they are filled with an opaque, granular, calcareous substance, and 

 very often are in direct connection on one side with dentinal canals, and on 

 the other side with the bone-corpuscles of the cement. Sometimes this inter- 

 mediate layer is very finely granular, and the spaces between the grains are 

 exceedingly small. The cement proper commences outside of this layer, and 

 its canaliculi rarely come into direct connection with the dentinal canals." 



From W. Waldeyer * I quote : " The chief components of dentiiw are a very 

 firm matrix, analogous to compact bony tissue, and extremely fine, frequently 

 branched, fibers, the dentinal fibers of Tomes and Kolliker, which occupy 

 fine canals, the dentinal canals traversing the matrix. The dentinal fibers 

 are enormously elongated processes of the so-called dentinal cells, or cells of 

 the dentinal pulp (odontoblasts). The dentinal fibers constitute the soft 

 parts of the dentine. They do not lie in direct contact with the hard matrix, 

 but are invested by a sheath, the dentinal sheath of E. Neumann, which is 

 intimately connected with the matrix. As a general rule, each tube extends 

 from- the pulp-cavity to the enamel or cement, giving off, in its course, 

 numerous delicate, transverse branches. By means of these transverse 

 branches both the tubes and their contents the dentinal fibers anasto- 

 mose with each other. In regard to the mode of peripheric termination 

 of the dentinal tubuli, no positive conclusion can be drawn. It is not easy to 

 decide whether the fibers are present in the finest peripheric ramifications of 

 the tubules. A direct passage of the dentinal tubuli into the enamel does not 

 occur." On enamel : " It consists of rather elongated prisms, about three to 

 five mm. long, which are called enamel-fibers, or enamel-prisms. The dark, 

 transverse striae and slight varicosities, which, especially after the addition of 

 very dilute hydrochloric acid, occur at regular distances from one another in 

 the isolated prisms of enamel, are very remarkable. If the treatment with 

 hydrochloric acid be continued for some time longer, the fibers split, in the 

 direction of the clear transverse lines, into small cubic fragments of nearly 

 equal size, three to four mm. The enamel fibers lie in close contact with each 

 other, without any demonstrable intervening substance. The cuticula (per- 

 sistent capsule of Nasmyth) forms an extremely resistent investment, not 

 more than one-half mm. in thickness, covering the external portion of the 

 teeth, and disappearing wholly when they are mature." On cementum : " The 

 cement is a true bony structure essentially belonging to the periosteum of the 

 alveolus, and in man and many vertebrates forms a thin investment of the 

 fangs of the teeth. The lacunas are for the most part large. When the 

 cement is extremely thin, however, they may be entirely absent, and it then 

 presents on section a perfectly homogeneous and vitreous appearance. A 

 similarly very hard lamella, destitute of lacunse, occurs also in the outermost 

 portion of the thick layers of cement." 



E. Magitot t says : " The dentine is bounded throughout its whole external 

 surface by a continuous layer of dark granulations, very numerous and of 

 various form. This granular layer, subjacent to the enamel and cement, was 

 taken by Retzius and J. Miiller for a mass of bony corpuscles, in which ter- 



* Strieker's " Manual of Histology," 1872. t " Treatise on Dental Caries," 1878. 



