354 REAGENTS AND THEIR PREPARATION [H. X 



95 % or absolute alcohol and 50 cc. of sulphuric ether. This may be 

 used before deparaffining or preferably afterward. See 622. 



557. Congo red. Water 100 cc., Congo red J gram. This is 

 a good counter stain for hematoxylin. 



558. Congo-glycerin. For mixing with and staining isolation 

 preparations (517) and for a mounting medium this is an excellent 

 combination. It is particularly good for nerve cells. 



559. 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 10 days, depending on the object. 

 One can tell when the decalcification is complete 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. 



560. Dissociating Liquids. These liquids are for preserving 

 the tissue elements or cells and for dissolving or softening the inter- 

 cellular 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 w is mounted. One may find it 

 desirable to use (d) with all the methods. 



(1) Formaldehyde dissociator. Strong formalin (40% formalde- 

 hyde 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 i cc. Normal salt 

 solution 9 cc. It usually requires from i 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 used especially for muscular tissue. It takes from i to 3 days, 

 depending on the temperature. The nitric acid gelatinizes the con- 

 nective tissue. Wash out the acid with water for a few minutes. 

 Preserve in 2% formaldehyde. 



