io PRACTICAL HISTOLOGY. 



2. COLUMNAR EPITHELIUM. 



A. FRESH COLUMNAR EPITHELIUM. 



PREPARATION. Slit open the small intestine of a cat just killed, and wash away the 

 mucus covering its inner surface with a stream of f per cent, solution of common salt, scrape 

 the mucous surface and diffuse the scraping in the same strength of salt solution, and after 

 breaking it up with needles, cover and irrigate with magenta solution (p. xliv). 



EXAMINATION (H). A large number of elongated, narrow, or columnar cells are to be 

 seen. Each cell is finely granular and contains a nucleus which is stained red. One end of 

 the cell the attached end is somewhat pointed, while the free end presents a narrow, clear, 

 unstained hem, or border, marked with fine vertical lines or striae. This indicates that the 

 free end of each cell is covered by a transparent plate or disc. When several cells adhere to 

 each other, and their free ends, instead of their sides, are presented to the observer, a fine mosaic 

 is observed. The intercellular substance is small in amount, mapping out the individual cells 

 one from another, while in the centre of each area a red nucleus is seen (PL II., Fig. 4). In 

 addition, here and there so-called 'chalice' or 'goblet' cells are seen (PI. II., Fig. 6). These 

 have a cup-shaped appearance, are devoid of the clear border and contain a nucleus sur- 

 rounded by a small quantity of protoplasm near the lower pointed extremity of the cell, whilst 

 the greater part of the body appears to be clear and looks as if it were empty. This is not 

 to be preserved ; but, in order to obtain permanent preparations, the small intestine may be 

 treated in one or other of the following ways. 



B. PERMANENT PREPARATIONS. 



PREPARATION (a). Place a square half-inch of the intestine in 40 to 60 cubic 

 centimetres of a one per cent, solution of ammonium bichromate for two days. 



(V) A similar piece in dilute alcohol (i rectified spirit to 2 water) for twenty-four hours. 



(c) A similar piece in a few c.c. (5-10) of a one per cent, solution of osmic acid (p. xlvi) for 

 half an hour. 



Any of these may be used for preservation, but in every case the specimen must first be 

 steeped in water for half an hour or longer, to get rid of the hardening reagent. 



EXAMINATION (H). Scrape off a little of the mucous surface of a or b, place it on a 

 slide, and break it up with needles. Add a drop of picrocarmine, and allow it to stain for fifteen 

 minutes. Remove the surplus staining-fluid, add a drop of glycerine, cover and examine. 



In either case columnar and chalice cells similar to those already described will be found, 

 except that in a each cell will be yellow with a red nucleus, while in b the red nucleus will be 

 seen to contain what has been described as a nucleolus. If c be similarly treated, it must be 

 left in the picrocarmine for twenty-four hours, when the same appearances are seen as in a, 

 with this addition that if the cells contain any fatty particles, these are blackened. These 

 three preparations when sealed as described (p. xlix) are permanent. 



Columnar Epithelium from the small intestine of a newt. Where the cells are relatively 

 large, and show very distinctly the intra-cellular and intra-nuclear plexus. 



PREPARATION. Kill a newt and place its small intestine in a few c.c. of a five per cent. 



