ENAMEL 87 



to that of the tubes, but quite unstained. The fuchsin 

 method before referred to was adopted in this investigation, 

 and the stain was found to enter the striae from the outer 

 surface of the enamel and penetrate them to their termina- 

 tions. The prisms of the enamel are easily distinguished 

 from the tubes, showing that the enamel columns and the 

 strise are not identical, as has been suggested. 



In Sargus ovis, the Sheep's-head fish of the United States, Sargus. 

 the tubes, which are very strongly marked, pass into the 



f 



^'- *R? 



FIG. 41. Osteodentine tooth of Lamna cornubica (Porbeagle Shark) 

 Osteodentine centre ; tubes radiating from medullary channels, e. Enamel. 

 Fuchsin stain by capillary attraction. ( x50.) 



enamel at right angles to its surface, and about half-way 

 across its width bend right and left, crossing one another on 

 its inner third, and terminating at a line of dense calcifica- 

 tion which forms a dark band following the contour of the 

 dentine surface, and separated from it by a narrow clearer 

 space. The tubes do not reach the dentine in any part 

 (fig. 42). The very complicated pattern in drawings and 

 photographs of Sargus enamel is only due in part to the 

 ramifications of the tubes, which can be easily followed 

 in the stained preparations, for the densely calcified band 

 of enamel near the dentine is formed by the exceedingly 

 intricate and complicated course of the prisms. 



