222 MICROSCOPICAL RESEARCH IN THE 



b. Acetic acid added by drops to solution <?, while shaking, until 

 the colour is about the same as that of Beale's carmine. 



c. Solution b left standing twenty-four hours, then turned off 

 and filtered. 



This solution, which is a modification of Schweigger-Seidel's 

 acid carmine, is not recommended for colouring i7i toto. It colours 

 sections in ^-3 minutes diffusely, and hence, after washing in 

 water, they are placed for a few minutes in alcohol (50 or 70 per 

 cent.), to which a drop of hydrochloric acid has been added ; then 

 transferred to pure alcohol. 



(3) Borax Carmine.* — a. An aqueous solution of borax (4 per 

 cent.) and carmijie, heated till the carmine is dissolved. 



b. Solution a mixed with 70 per cent, alcohol in equal parts^ 

 left standing twenty-four hours, and filtered. 



This fluid may be used for colouring objects in toto. After 

 staining, the objects are to be washed in 35 per cent, alcohol, to 

 which a little hydrochloric acid has been added (4-6 drops to 

 100 ccm.), and allowed to remain there until the colour has been 

 sufficiently removed. They are next passed through successively 

 higher grades of alcohol for hardening. 



(4) Alcohol Carmine. — A teaspoonful of carmine dissolved, by 

 heating about ten minutes, in 50 ccm. of 60-80 per cent, alcohol, 

 to which 3-4 drops of hydrochloric acid have been added, then 

 filtered. 



Objects coloured in this fluid should not be washed in water, 

 but in alcohol of a grade corresponding to that of the solution. 



For diluting alcoholic solutions of carmine, alcohol of the 

 same strength must always be used. 



6. Aniline Dyes. — As a rule, aniline colours and the many 

 others obtained recently from tar by chemical processes, cannot be 

 used for staining objects in toto, and are therefore not much em- 

 ployed in the Zoological Station. In very small objects and sec- 

 tions already cut, very excellent results can be obtained by the 



* Dr. Mayer prepares, for some purposes, borax carmine of 50, 60, or 70 per 

 cent. That of 70 per cent, contains little carmine, V)ut is well adapted to staining 

 delicate objects that would suffer if exposed to weaker solutions. Boiling alcohol 

 (50 per cent, or 60 per cent.) dissolves about i per cent, carmine and i per cent, 

 borax. 



