472 STRUCTURE AND DEVELOPMENT OF TEETH, W. WALDEYER. 



crown of the tooth, usually following its contours with accuracy. 

 Its surface, especially at the sides, exhibits very fine, nearly 

 parallel, transverse striae (Czermak), which are probably re- 

 ferrible to the papillary structure of the enamel organ (see 

 this). Coarser projections with deep grooves, which have like- 

 wise been described by Czermak, must be regarded as patho- 

 logical formations. 



In young teeth, examined at that stage in which the enamel 

 is still soft and capable of being cut with a knife, it is easy to 

 demonstrate that it consists of rather elongated prisms of 

 about 3 5 /i long, which are called enamel fibres, or enamel 

 prisms (see fig. 103, 4 and 5). It is impossible to avoid 

 perceiving a certain similarity in form between these and very 

 long columnar epithelial cells, like those which form the fibres 

 of the lens. This is especially obvious in fine transverse sec- 

 tions, which exhibit a delicate mosaic with six-sided areas. 

 After cautious treatment with dilute hydrochloric acid and 

 subsequent boiling in S 3 (Beigel (50), whose method other- 

 wise affords no special advantage), the enamel prisms can be 

 easily isolated in adults. Their extremities are often pointed 

 like a needle, which, however, appears to depend only on ir- 

 regular fracture. By the same means, also, it can be shown 

 that the prisms partly run in a straight direction, and partly 

 in curves ; but I have not been able to satisfy myself that 

 angular or zigzag curvatures occur, as stated by Czermak. 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 hydro- 

 chloric acid be continued for some time longer, the fibres split 

 in the direction of the clear transverse lines into small cubic 

 fragments of nearly equal size (3 4 ju). 



It still remains a question how the transverse bands are to be ex- 

 plained. The circumstance that they are generally absent, or at least 

 are not so well marked in young soft fibres, and that their relative 

 thickness nearly corresponds to the thickness of the fibres, has led 

 me (49) to express the opinion that they might proceed from the de- 

 cussation of the fibres. I am well aware of the grounds adduced by 

 Hertz (52) against this supposition, and which are assented to by 



