NUCLEUS OF EPITHELIUM-CELL. 



45 



bear on their basal or free ends spontaneously moving filaments, named 

 cilia; on ^vhich account this variety of epithelium is termed ciliated 

 (fig. 21). 



Fig. 21. 



Fiff. 22. 



Fig. 21. — Columnar Ciliated Epithelium Cells from the Hl-man Nasal Membrane; 



3IAGNIFIED 300 DIAMETERS. 



Fig. 22. — Diagram of Section of Stratified Epithelium, in which the under- 

 most CELLS ARE OBLONQ AND VERTICAL. 



"When the cells of an epithelium are arranged in several superimposed 

 layers instead of being in a simple layer, it is termed stratified : in 



Fig. 23. 



Fig. 23. — Epithelium of Conjunctiva of Calf. 



1, 2, 3, 4, 5, progressive flattening of the cells a.s they rise to the surface. The out- 

 line figures represent single cells from diflerent depths, viewed on their surface ; and at 

 4' and 5', edgeways. Magnified 410 diameters (chiefly after Henle). 



these cases it is commonly found that the lowermost layer is columnar 

 in sliape, and the uppermost scaly ; the intermediate strata presenting 

 transitions between these forms (figs. 22, 23). 



Tiie first three of the varieties here enumerated present local pecu- 

 liarities which make it convenient to describe them with the tissues or 

 organs with which they are associated. The ciliated epithelium, on the 

 other hand, being of nearly uniform character as regards situation, 

 vital properties and functional activity, can be most conveniently treated 

 of under one general head, and will therefore be considered here. 



It may first be remarked, however, that amidst these changes the 

 nucleus of the cell undergoes little alteration, and its characters are 

 accordingly remarkably uniform throughout (see figs.). It is round or 



oval, and more or less flattened ; its diameter measures from 



vth to 



TyVoth of an inch, or more. Its substance is insoluble in acetic acid, 



