422 HISTOLOGICAL TECHNIQUE. 



Borax-carmine is used for the staining of little masses of tissue 

 before they are embedded. It is a nuclear dye, giving the chromatin 

 a red color. It is useful when paraffin-embedding is to be employed 

 and it is desirable to restrict the manipulation of the sections to a 

 minimum. 



Small pieces of hardened tissues, not over 5 mm. thick, are trans- 

 ferred from distilled water to the undiluted dye and allowed to stain 

 for twenty-four hours, or longer. After staining they are immedi- 

 ately placed in an acid alcohol, prepared by adding 5 drops of con- 

 centrated hydrochloric acid to 100 cc. of 70 per cent, alcohol. The 

 tissue should not rest on the bottom of the vessel containing the 

 alcohol, but upon crumpled filter-paper, so that the extracted excess 

 of coloring-matter may sink to the bottom. If the acid alcohol 

 around the specimen becomes colored, fresh portions of alcohol 

 should be used. The treatment with acid alcohol is continued until 

 no more color is given off from the specimen. It is then transferred 

 to 90 per cent, alcohol, in which it should remain for twenty- 

 four hours, after which it can be subjected to the dehydration neces- 

 sary for embedding. 



5. Orth's Lithio-carmine. 



Carmine, " No. 40," 3 grams. 



Lithium carbonate, saturated aqueous solution, 100 cc. 



The solution of lithium carbonate is prepared by occasionally 

 shaking a mixture of distilled water and an excess of lithium car- 

 bonate. Twenty-four hours will suffice for the production of a 

 strong enough solution. The supernatant liquid is then filtered. 

 Carmine readily dissolves in this solution. For preservation a 

 crystal of thymol may be added. 



Lithio-carmine stains sections in about five minutes, and there is 

 no danger of overstaining. Like borax-carmine, it requires after- 

 treatment with acid alcohol. The sections should be transferred, 

 without intermediate washing, to 70 per cent, alcohol containing 1 

 per cent, of concentrated hydrochloric acid ; they may then be de- 

 hydrated, and, if desired, counterstained with picric acid during the 

 dehydration. 



6. Unna's Methylene-blue. 



Methylene-blue, 1 gram. 



Potassium carbonate, 1 " 



Distilled water, 100 cc. 



