50 BIOLOGY. [BOOK i. 



recalls a pavement of hexagonal bricks. In animals they clothe 

 the mucous membrane with many conduits, and play especially 

 the part of a protecting varnish. As related to them may be 

 regarded the epidermic cells. Other epithelial cells are cylindrical 

 or cylindro- conical. Sometimes the free surface of these cells is 

 furnished with fine and mobile cilia. In that case the epithe- 

 lium is called vibratile epithelium. 



We have besides to mention the globulous, the spherical 

 epithelium. We find it especially in the glands where its 

 function is to form, at the expense of the plasmas and the 

 blastemas, the special bodies destined to be secreted. 



Finally, we signalise here for the sake of remembrance the 

 muscular elements, distinguished into fibre-cells and into fibres 

 properly so called ; then the elements of the nervose tissue, fibres, 

 and cells. We shall have elsewhere to describe in detail the 

 form, the structure, the functions of these elements, which may 

 be characterised as aristocratic. 



