68 MICROSCOPIC ANATOMY OF THE TEETH 



ridge separating the two grooves. In these teased pre- 

 parations small detached fragments are seen which show 

 the concavo-convex form in cross-section (Plate III, fig. 4), 

 and occasionally, longitudinally broken-up prisms which 

 give still more certain evidence of the structure, as they 

 show that the broken end of the prism has the above- 

 described concavo-convex form (Plate III, fig. 3). Detached 

 fragments, in which the prisms have broken up in a trans- 

 verse or oblique direction, also give very instructive views 



/m 





FIG. 26. Enamel of molar of Asiatic Elephant. ( x 800. ) 



of this structure. In Plate III, fig. 10, the whole of one of 

 the arched prisms is seen in situ, with its concave margins 

 projecting free from the surrounding prisms. 



In many parts of "the sections not only have the prisms 

 the tile-like appearance above described, but they show 

 a serrated margin and appear as if grooved or ridged on 

 the surface, many of them bearing a curious resemblance 

 to the frond of a maiden-hair fern (fig. 25). 



In these transverse sections of the Elephant's molar, 

 where there are alternate areas of cement enamel and 

 dentine, the convexity of the prism is invariably directed 

 towards the dentine and never towards the cement on 



