EXPLANATION OF THE PLATES. 



The figures in this plate are magnified to the same extent as those of 

 most of the plates illustrating the work, viz. 670 diameters. 



PLATE XX. 



Fig. 1. Buccal epithelial cells in different stages of deve- 

 lopment, from their earliest condition, in which 

 they bear the form of mucous corpuscles, to their 

 fully developed state. For a representation of the 

 epithelial cells of the vagina and oasophagus, see 

 Plate "KILJigs. I and 2. 



2. Cylindrical or cuneiform epithelial cells taken from 

 the duodenum of a child seven days old : those of 

 the adult are in every respect identical ; the group 

 of angular cells at the inferior part of the figure 

 represents the summits of the cuneiform epithe- 

 lial cells. 



