DEVELOPMENT OF THE ENAMEL 



121 



of the enamel organ. Its intimate relations, however, with 

 the blood-vessels of the capsule would suggest that it serves 

 a much more important purpose. Dr. Paul says its ' chief 

 function seems to be the separation from the blood of the 

 constituents of enamel which are elaborated by the internal 

 epithelium ' (17). It would seem highly probable that this is 

 the function of these cells, at all events in the early stages 

 of calcification. The budding of the cells of the external 



FIG. 69. External epithelium of enamel organ of Macropus showing 

 elongated fusiform cells, e. External epithelium ; s. stellate reticulum. 

 (x350.) 



epithelium, to be presently described, would also indicate 

 a more important function of this layer than is usually 

 ascribed to it. The blood-vessels in the follicle are in close 

 relation with the external epithelium of the enamel organ, 

 and in places it is seen to be discontinuous, and these blood- 

 vessels are distinctly in contact with the cells of the stellate 

 reticulum (fig. 70). 



In marsupials they have been seen to penetrate the ex- 

 ternal epithelium in many instances and to enter the stellate 

 reticulum. In the Wallaby (Macropus billiardieri) they have 

 been shown to do so by Marett Tims and Hopewell Smith 



