23 



LESSON VII. 



COLUMNAR AND CILIATED EPITHELIUM, AND 

 TRANSITIONAL EPITHELIUM. 



1. TAKE a piece of rabbit's intestine which has been two days in chromic 

 acid solution (1 part chromic acid to 2,000 normal salt solution). Scrape the 

 inner surface with a scalpel, break up the scrapings in a drop of water on a 

 slide. Add a small piece of hair to avoid crushing, and cover the preparation. 

 Sketch one or two columnar cells and also a row of cells. Measure two or 

 three cells and their nuclei. 



To keep this preparation, add a drop of dilute hsernatoxylin (1 drop of the 

 ordinary solution to half a watch-glass-ful of distilled water) at one edge of the 

 cover-glass. When the haernatoxylin has passed in and has stained the cell- 

 nuclei, place a drop of glycerine at the same edge, and allow it slowly to diffuse 

 under the cover-glass. Cement this another day. 1 



2. Break up in glycerine a shred of epithelium from a piece of frog's 



intestine that has been treated with osmic acid, and has subsequently 



macerated in water for a few days. The cells easily separate on tapping the 



' cover-glass. They are larger than those of the rabbit and exhibit certain 



points of structure better. Measure and sketch one or two cells. 



The cover-glass may be at once fixed by gold size. 



3. Prepare the ciliated epithelium from a trachea that has been in 

 bichromate of potash solution (^ per cent.) for two days, in the same way as in 

 1. Measure in one or two of the cells (a) the length of the cell, (6) the 

 length of the cilia, (c) the size of the nucleus. Sketch two or three cells. 



This preparation is to be stained and preserved as in 1. 



4. Make a similar teased preparation of the epithelium of the urinary 

 bladder. Observe the large flat superficial cells, and the pear-shaped cells 

 of the second layer. Measure and sketch one or two of each kind. 



Stain and preserve as in 1 and 3. 



Columnar epithelium. The cells of a columnar epithelium (fig. 21) 

 are prismatic columns, which are set closely side by side, so that when 

 seen from the surface a mosaic appearance is produced. They often 

 taper somewhat towards their attached end, which is generally trun- 

 cated, and set upon a basement membrane. Their free surface is 

 covered by a thick striated border (fig. 22, str), which may some- 

 times become detached in teased preparations. The protoplasm of 

 the cell is highly vacuolated or reticular, and fine longitudinal striae 

 may be seen in it, which appear continuous with the striae of tht 



1 Gentian-violet solution (see Appendix) may be employed instead of ha-ma 

 toxylin. 



