78 MICROSCOPIC ANATOMY OF THE TEETH 



advancing upon the odontogenic zone. The union of the 

 enamel and dentine does not, however, appear to be a very 

 intimate one, but in some mammalian teeth which have to 

 bear great strain a much more perfect union between the 

 two tissues is seen. 



In a transverse section of the molar of the elephant, 

 which is made up of plates of enamel, dentine, and cement, 

 little thorn-like processes are seen projecting into the enamel 

 from both the dentine and the cement, forming a complete 

 interlocking of the tissues (fig. 35). This was first recorded 

 by Professor Miller and Dr. Dieck in the Asiatic elephant. 

 Miller also found the same structure, although not so highly 

 developed, in the African elephant, and described a similar 



FIG. 35. Transverse section of molar of Elephant showing the thorn- 

 like processes. ] E. Enamel ; D. dentine ; C. cement. 



condition in the enamel of the Wart-hog and Hippopotamus, 

 in which animals, however, the thorn-like processes proceed 

 only from the cement and not from the dentine. 



Certain spaces, the so-called ' spindles ', are found within 

 the enamel especially at, and around, the summits of the 

 dentine cusps (figs. 36 and 37). 



These are irregular areas of a more or less tubular form 

 and are found, often in great abundance, in most human 

 teeth. They mostly project at right angles to the dentine 

 surface. 



Waldeyer and Hertz denied the existence of these spindles 

 on the ground that the appearances were produced by the 

 obliquity of the sections or by fissures in the enamel, but 

 it is difficult to understand how these observers can have 

 arrived at such a conclusion after the examination of even 

 a few good ground sections of human enamel. There appears 



