538 THE MICROSCOPE. 



Tesselated epithelium is the simplest form, and, as its 



name implies, resem- 

 bles flags of pavement, 

 overlapping each other 

 at their edges. They 

 assume, more or less, 

 the polygonal form, and 

 their size varies in the 

 different serous mem- 

 branes. The cells of the 

 pericardium, or cover- 

 ing membrane of the 

 heart, are much smaller 

 than those of the cover- 

 ing membrane of the 

 Fi s- 273 - lungs, or the serous 



1, Simple isolated cells containing reproductive surface of the COrnea, 

 granules. 2, Mucous membrane of stomach, r\ or . ry . 



showing nucleated cells. 3, One of the tubular "* UI1 bOIlJ 

 follicles from a pig's stomach. 4, Section of a -y?Q have many 

 lymphatic, magnified 50 diameters. . ., , . .3 .,, . 



in the skin it will be 



found of comparatively great consistence. If a vertical 

 section of such be made, and viewed under the microscope, 



it will be seen to be 

 composed of number- 

 less layers, shown in fig. 

 272. The skin taken 

 from the sole of the 

 foot, in consequence of 

 the continued pressure 

 there experienced, pre- 

 sents this distinctly 

 stratified appearance. 

 These layers of cells 

 are held together by 

 intercellular substance, 

 which exists in quanti- 



Fig. 274. (i) ^ es m *^ e epithelium 



of the mucous mem- 

 branes ; if the epithelium is taken from these membranes, 



(1) a is a diagram of a portion of the involuted mucous membrane, showing 

 the continuation of its elements in the follicles and villi, with a nerve entering 



