40 MICROSCOPICAL RESEARCH 



The use of hydrocliloric acid in process 2 is to remove the surplus stain out 

 of the sections, and if the sections are thick and deeply stained the acid wash 

 must be prolonged until the colour is reduced to the required tint. The acid 

 should never be used if the colour of the section can be reduced to the proper 

 tint by the use of alcohol alone. Two drops of acid to one ounce of alcohol is 

 a useful standard to work with, but in many cases six to eight drops to the 

 ounce will be required; on the other hand the merest trace of acid will remove 

 some stains completely from the sections. Carmine and Hsematosylin are the 

 two chief stains for which the acid should be used; nearly all other stains may 

 be reduced to the required tint by the use of alcohol alone. 



No. 2. BORAX CARMINE.— Woodward. 



Best carmine 3 grams. 



Borax 12 grams. 



Water 480 cc. 



Alcohol 92% 480 cc. 



Mix the ingredients and filter for use. The first filtrate. 



The crystals left on the filter paper must now be washed into 960 cc. of 

 water, dissolve by heating to boiling point ; when cold filter for use. The second 

 filtrate. 



The first filtrate is a weak stain and slow in its action, but it is specially 

 useful for staining entire specimens such as pinnae of ferns, spikes of selaginella, 

 etc., and is specially applicable for staining marine zoological specimens. 



The second filtrate is more rapid in its action, and is useful for staining 

 sections or specimens that are to be mounted in glycerine jelly; the colour being 

 practically permanent in that medium. 



Manipulation for the First Filtrate. 



1. Pour off the alcohol and cover the specimens with the stain, and allow to 

 stand from one to six or eight hours, according to the size and density of the 



