■CH. /X] PREPARATION OF REAGENTS 275 



All collodion solutions should be kept well corked or the ether will evapo- 

 rate, also some of the alcohol, and leave the soluble cotton as a kind of jelly. 



? 395- Collodion for Cementing Sections to the Slide. — This is a %% so- 

 lution made by adding % gram of soluble cotton to 50 cc. of 95% or absolute 

 alcohol and 50 cc. of sulfuric "ether. This may be used for spreading on the 

 sections before deparaffining or preferably afterward. See \ 450. 



I 396. Congo Red. — Water 100 cc, Congo red ^ gram. This is a good 

 counter stain for hematoxylin. 



\ 397. Congo-Glycerin. — For mixing with and staining isolation prepara- 

 tions ( \ 357-361) and for a mounting medium this is an excellent combina- 

 tion. It is particularly good for nerve cells. 



\ 398. Decalcifier. — For removing the salts of lime from bone etc. One 

 must first fix and harden the tissue by some approved method. 67% Alcohol 100 

 cc; strong nitric acid 3 cc. Change two or three times. It takes from 3 to 16 

 days depending on the object. One can tell when the decalcification is com- 

 plete by inserting a needle. If there is no gritty feeling the work is done. 

 Then wash a few minutes in water and transfer to 67% alcohol. Then after 24 

 hours use 82% alcohol. It is usually better to section by the collodion method. 

 Tissue is liable to deteriorate after being decalcified, so section it soon. 



\ 399. Dissociating Liquids. — These liquids are for preserving the tissue 

 elements or cells and for dissolving or softening the intercellular substance so 

 that the cells may be readily separated from their neighbors. The separation 

 is accomplished by (a) teasing with needles ; (b) shaking in a liquid in a test 

 tube ; (c) scraping with a scalpel and crushing with the flat of the blade ; (d) 

 by tapping sharply on the cover-glass after the object is mounted. One may 

 find it desirable to use (d) with all the methods. 



(1) Formaldehyde Dissociator. — Strong formalin (40% formaldehyde gas 

 in water) 2 cc. Normal salt solution 1000 cc. One can begin work within % 

 hour and good results may be obtained after 2 to 3 days immersion. Excellent 

 for epithelia and for nerve cells. 



(2) Miiller's Fluid Dissociator. — Miiller's Fluid 1 cc. Normal salt solu- 

 tion 9 cc. It usually requires from 1 to 5 days for epithelia to dissociate in this. 

 The action is more rapid in a warm place. 



(3) Nitric Acid Dissociator. — Nitric Acid 20 cc. Water 80 cc. This is 

 nsed especially for muscular tissue. It takes from one to 3 days depending 

 on the temperature. The nitric acid gelatinizes the connective tissue. Wash 

 out the acid with water. Preserve in 2 % formaldehyde. 



\ 400. Elastic Stain. — For staining elastic substance the Resorcin basic- 

 fuchsin-Iron-Chlorid of Weigert is available. The stain is prepared as fol- 

 lows. 



Basic Fuchsin 2 grams. Resorcin 4 grams. Water 200 cc. Boil for 

 several minutes (5 to 10). Add to the boiling mixture 25 cc. of a 30% aqueous 

 solution of chlorid of iron (Fe CI 6). Boil for 3 to 10 minutes then add a 

 saturated solution of iron chlorid until the color is all precipitated. Try the 



