DEVELOPMENT OF THE ENAMEL 



125 



A specimen fixed in formol and cut in gum on the 

 freezing microtome will, when mounted in glycerine or 

 Farrant solution, give quite a different picture, and one that 

 with little doubt gives a much better indication of the real 

 structure. 



Such a preparation of the stellate reticulum (fig. 74) 

 of a mammalian enamel organ shows that it is made 

 up of large cells, showing under high powers of the micro- 

 scope a delicate reticulated structure with oval or round, 



FIG. 73. Stellate reticulum. Macropus. (x600.) 



very conspicuous nuclei, which in well-stained preparations 

 also show one or more nucleoli. These cells are connected 

 by Abroad processes with one another and by finer thread-like 

 processes, giving to the whole structure its characteristic 

 stellate appearance. The intervals between the cells are 

 filled with a gelatinous or colloidal material which shows 

 no visible structure, but takes a very faint stain, showing 

 that these spaces are not empty, even in the microscopical 

 preparation. Leon Williams considers that the stellate 

 structure is simply the intercellular substance which is left 

 after the removal of the cell contents, and that the stellate 

 appearance is due to the persistence of the slightly modified 

 cell wall. It would appear advisable, however, to confine 



