IV.] 



EPITHELIUM AND ENDOTHELIUM. 



125 



As endothelium, it consists of a single layer of flattened squamous 

 transparent cells united to each other at their edges by means of a 

 cement substance. 



(B.) As stratified squamous epithelium, it covers the skin (epi- 

 dermis), and lines the following cavities and surfaces : mouth, 

 pharynx (lower half), oesophagus, conjunctiva, over anterior surface 

 of cornea, vagina, and lower half of cervix uteri, and entrance of 

 urethra. 



I. Isolated Squamous or Scaly Epithelium Cells. With the 

 finger-nail or a small section-lifter gently scrape the inner surface of 

 the lip, place the scrapings on a slide, add a drop of saliva, 

 skimming off any air-bubbles with a needle, cover, and examine. 



1. Squames (H). (a.) Observe large flat plates or squames 

 floating in the field, either singly or in groups ; the cells of the latter 

 may be united by their edges, or by their edges and surfaces. 

 Select a single squame seen on the flat. IS T ote its large size, being 

 five to ten times broader than a red blood-corpuscle ; its polygonal 

 shape ; the colourless, transparent, and, it may be, slightly granular 

 body of the cell, and the small oval excentrically-placed nucleus. 



(b.) On some of the cells fine lines may be seen, some of them 

 due to folds, but most of them to facets, indicating that the cell 

 has been overlapped and slightly indented 

 by its neighbour. Select a group of cells 

 where the cells can be seen adhering to each 

 other by their edges and surfaces, as the 

 squames occur in several layers. It is well 

 also to look for a cell seen edgeways, to 

 observe that it is really a flat plate (fig. 84). 



(c.) Not unfrequently fungi, such as 

 bacteria, may be seen adhering to the 

 squames. 



(d.) Salivary Corpuscles may be seen. 

 They are sharply-defined spherical cells, pro- 

 vided with a membrane, and about the size FlG 84 ._c e iis of stratified 

 of a colourless blood-corpuscle. They contain 

 fine granules, which in the fresh condition 

 of the corpuscles may be seen to exhibit 

 Hrownian movement (Lesson I. 6). Each cell may contain one 

 small, spherical, excentrically-placed nucleus, or sometimes two 

 nuclei may be present. They seem to be leucocytes distended with 

 fluid. 



2. Magenta. Irrigate the preparation with a watery solution of 

 magenta (p. 74), which stains deeply the nuclei of the squames and 

 salivary corpuscles, while tho po,ri-nuclear parts of these cells are 

 less deeply stained. As the magenta contains alcohol, the latter 



Sqnamous Epithelium de- 

 tached from the Month. 

 s. Salivary corpuscles. 



