APPENDIX 309 



Borax carmine (Grenacher). To 100 c.c. of a 4 p.c. aqueous 

 borax solution add 2 '5 grams carmine. Shake at intervals for 

 2 to 3 days. Add 100 c.c. 70 p.c. alcohol and, after 1 to 2 days, 

 filter. 



Pieces of tissue, or sections stained with this, are treated 

 with acid alcohol. 



Comparison of carmine stains. Bourne's picrocarmine is the 

 most generally useful for students ; and perhaps borax carmine 

 for staining in bulk. 



Methylene blue, toluidin blue, thionin, saffranin, Spiller's 

 purple. 



a. An aqueous solution is made of such strength that a 

 section when placed in two or three drops in a watch-glass can 

 just be seen. This stains in a minute or two, the section is 

 mounted in water; if overstained, the excess is taken out by 

 30 p.c. alcohol. The section may be mounted in glycerine tinged 

 with the staining agent, but in a varying time the stain becomes 

 diffuse. 



b. The section is stained in a '5 to 1 p.c. aqueous solution 

 for half-an-hour to a day, passed through alcohols and mounted 

 in balsam ; if the period of staining has been short, the stay in 

 alcohol requires careful attention in order to obtain the proper 

 degree of decolourization. 



c. A. solution is made in 75 p.c. alcohol, the strength being 

 tested as above. The sections are left in this for a day, then 

 decolourized to the required extent with 75 p.c. and stronger 

 alcohols. A saturated solution of the substance in absolute 

 alcohol plus an equal volume of water is used by some observers, 

 but the advantage hardly seems sufficient to make up for the 

 expense. 



With these stains, cedar- wood oil or xylol should be used to 

 clear the sections, and not clove oil or turpentine. 



For the method of using methylene blue cp. p. 18 (basophil 

 granules of leucocytes); p. 74 (connective tissue cells); p. 117 

 (basophil granules of nerve-cells); pp. 125, 321 (nerve-endings). 

 Thionin is especially used to stain the mucous cells of the 



