EPITHELIUM AND ENDOTHELIUM. 



ADDITIONAL EXERCISES. 



13. Pogiel's Methylene-Blue Method. Place any fresh membrane, e.g., 

 omentum, mesentery, capsule of kidney, in a 4 per cent, solution of methylene- 

 blue in normal saline. Allow it to stain for ten minutes or so. Wash it twice 

 in a saturated watery solution of picrate of ammonia and examine in glycerine. 

 The outlines of the cells are stained of a purplish colour. This method may 

 be used instead of the silver method to demonstrate the existence of endo- 

 thelium on any surface, e.g., on tendons (rat) in blood- or lymph-vessels. It 

 is also used to demonstrate lymph-spaces. 



14. Sections covered by or consisting of epithelial cell structures may 

 be stained in a weak watery solution of benzo-azurin. This stain is not 

 removed by alcohol, and the sections can be mounted in balsam. Or benzo- 

 purpnrin (B. ) may be used. This gives a reddish stain, any excess being 

 removed by alcohol rendered feebly alkaline, e.g. , by lithium carbonate. 

 Benzo-azurin stains connective tissue of a bright blue. 



LESSON V. 



COLUMNAR, SECRETORY, AND TRANSITIONAL 

 EPITHELIUM. 



Columnar Epithelium lines the mucous memhrane of the ali- 

 mentary canal from the cardiac orifice of the stomach onwards; 

 the greater part of the ducts of the glands opening into it ; other 

 gland ducts. 



II. Columnar Epithelium. Slit open the small intestine of a 

 rabbit or a cat t ;w*tf killed. Wash the mucous surface with normal 

 saline to remove any adherent particles. 



1. Fresh Condition (H). With a scalpel gently scrape the 

 mucous surface and transfer what is on the scalpel to a drop of 

 normal saline solution on a slide. Diffuse the scrapings in this 

 fluid, and t< prevent the pressure of the cover-glass, place in the 

 iluiil a hair half-an-inch in length. This preparation is not to he 

 preserved. 



(.) Observe numerous columnar epithelial cells, a few isolated, 

 but most of them adhering together. Side View of the Cells. 

 Select an isolated cell, notice its columnar form, usually tapering 

 to a blunt point at one end, while the body of the cell is faintly 

 granular, and contains a clear oval nucleus. The free, broad end 

 is covered wilh a highly retractile disc seen on edge as a narrow 

 retractile band with fine vertical striae in it (fig. 92). 



