130 MICROSCOPIC ANATOMY OF THE TEETH 



layer (fig. 77, a, and Plate IV at a). This, the most constant 

 and most important structure of the enamel organ, forms its 

 innermost layer, and before calcification has commenced lies 

 in immediate contact with the dentine papilla. The cells 

 of this layer are columnar in shape, with very distinct oval 

 nuclei, which lie for the most part at the distal extremity of 

 the cell, the end farthest removed from the point where the 

 earliest deposit of calcific matter takes place. Here and 

 there, however nuclei are to be seen near the proximal ends 



FIG. 76. Enamel of Rat. s. Papillae and vessels in the enamel organ ; 

 a. ameloblasts ; e. enamel; d. dentine. ( x 250.) 



of the cells, and in late stages of calcification in marsupials 

 very many nuclei occupy this position, and are crescentic 

 in shape, as first pointed out by C. S. Tomes (26), who also 

 described the horns of the crescent as looking as if they 

 were continued into filamentous processes. Many prepara- 

 tions of the author's seem to show that there can be little 

 doubt that these processes are connected with the nuclei 

 (fig. 85). 



The nuclei of the ameloblasts have very distinct nucleoli, 

 and show a fine nuclear network in suitably stained pre- 

 parations, and the body of the cell is occupied by very 

 delicate strands of protoplasmic fibres arranged chiefly in 



