XIT IXTRODUCTIOX. 



hoek were not prepared to appreciate them ; besides 

 they could neither repeat nor confirm them, for his 

 means of observation were pecuharly his own; and 

 hence it has happened that, with the exception of the 

 learned Portal,* they have either escaped notice, or 

 have been designedly rejected by all anatomists until 

 the time of the confirmation of their exactness and 

 truth by Purkinje in 1835." 



Continuing tlie subject, Prof. O'ven further says of 

 the three constituent parts of teeth— dentine, enamel, 

 and cement — beginning with 



THE DEK-TIK-E. 



^•Purldnje states that the dentine consists, not of 

 superimposed layers, but of fibers arranged in a homo- 

 geneous intermediate tissue, parallel with one another, 

 and perpendicular to the surface of the tooth, running 

 in a somewhat wavy course from the internal to the 

 external surface, and he believed these fibers to be 

 really tubular, because on bringing ink into contact 

 with them, it was drawn in as if by capillary attraction. 



" On the publication of this discovery, it was imme- 

 diately put to the test by Prof. Miiller, by whom the 

 tubular structure of the denthie was not only con- 

 firmed, but the nature and one of the offices of the 

 tubes were determined. He observed that the white 

 color of a tooth was confined to these tubes, which were 

 imbedded in a semitransparent substance, and he found 

 that the whiteness and opacity of the tubes were re- 

 moved by acids. On breaking a thin lamella of a tooth 

 transversely with regard to its fibers, and examining 

 the edge of the fracture, Miiller perceived tubes pro- 



* " Histoire de I'Anatomie et de la Cliirurgie," Paris, 1770. 



