LABORATORY DIRECTIONS. 457 



remove several inches of the colon, clean carefully 

 by passing water through it, and then distend the 

 piece with 25 per cent, alcohol, ligating both ends. 

 Next day open the bowel and make light scrapings 

 from the mucous surface and place these in a vial 

 containing equal parts of alcohol (50 per cent.) and 

 glycerin. Shake the vial and the cells will dis- 

 seminate throughout the fluid. The 25 per cent, 

 alcohol dissolves the cement that holds these epi- 

 thelial cells together. If desired, a little stain may 

 be added to the glycerin preparation. 



The epithelium of the bladder may be obtained in 

 the same manner, by distending the organ with 25 

 per cent, alcohol; also, the ciliated cells of the 

 trachea, although in this case no distention is 

 possible. All these cells come away very easily, 

 and the scraping must be carefully done. 



Tubules of the kidney are readily obtained by 

 treating small pieces with acid. In twenty-four 

 hours, remove the pieces to equal parts of alcohol 

 and glycerin, and shake. A drop of this will show 

 all forms of tubules and glomeruli. The former are 

 practically equivalent to epithelial casts, clinically 

 so important in urinary analysis. 



The caustic potash reaction is more rapid. Pieces 

 of tissue may be treated with this on the glass slide 

 and examined in the fluid. Care must be observed 

 that the alkali does not get on the lens of the micro- 

 scope. 



IV. To Prepare Tissue for Sectioning in Celloidin 

 or Paraffin. 



i. Fixing and Hardening. Fixing consists in 



