338 MICROSCOPIC ANATOMY OF THE TEETH 



nuclei exhibit the ordinary nuclear structure with one or 

 two strongly marked nucleoli. 



As stated in describing the follicle, amitotic division of the 

 nucleus without division of the cell body is apparent in many 

 of these cells in the floated preparations, corresponding to 

 the same appearances in the cells of the follicle itself (fig. 225). 

 It is interesting to note that according to several authorities, 

 and as stated by Dahlgren and Kepner, ' In nearly all 

 stratified epithelia, especially in the higher vertebrates, the 

 nucleus divides by mitosis to increase the number of cells, 

 but it changes to amitosis without a division of the cell body 

 in the latter part of the cell's life. The probable object is 



FIG. 225. Amitotic division in the cells of Nasmyth's membrane. 

 Floated preparation. Camera lucida drawing ( x 800.) 



to enlarge the nuclear surface for increased metabolism, the 

 formation of keratin in this case ' (2). 



Wilson says (12), ' Those cells that divide amitotically 

 are on the road to ruin/ and quotes Von Rath, who reached 

 the conclusion that * when once a cell has undergone amitotic 

 division it has received its death warrant it may indeed 

 continue for a time to divide by amitosis, but inevitably 

 perishes in the end '. 



Certain areas of the membrane show accumulations of cells 

 arranged more or less concentrically, and apparently sur- 

 rounded by a delicate limiting membrane (fig. 226). Dense 

 concentric bodies are also seen in parts of the membrane form- 

 ing definite cell nests (fig. 227) ; these are very opaque and 

 stain badly, and apparently represent a late stage in the de- 

 generation and keratinization of the cells. Cells arranged in 



