CHAPTER XLVIII 



GENERAL STAINING 



1287. The stains used are mostly the standard solutions of 

 single dyes. Aqueous solutions, e.g. of eosin, carmine, gentian or 

 crystal violet, methylen blue, anilin blue, picric acid, are com- 

 monly 1 or 2 per cent, solutions in distilled water. Solutions of 

 crystal or gentian violet in anilin water (saturated aqueous 

 solution of anilin oil, prepared by shaking and filtering) stain 

 more densely but do not keep so well. The haematoxylins most 

 used are Heidenhain, Delafield, Erhlich and Kleinenberg. Alco- 

 holic solutions are generally 1 per cent, and are made up in 70 

 per cent, alcohol, e.g. fuchsin, light green, methyl or iodine green, 

 Bismark brown, crystal or gentian violet, alcoholic eosin or 

 erythrosin, auramine, phloxine (Magdala red). Safranin O is 

 usually used as a 1 per cent, solution in 50 per cent, alcohol, pre- 

 pared with distilled or anilin water (Zwaardemaker, Zeit. 

 wiss. Mik., iv, p. 212). Taylor adds 0-25 per cent, auramine 

 to solutions of safranin and light green if the colour tone is too 

 cold. 



Freehand sections can usually be well stained using much 

 shorter periods in the stains than are indicated for microtome 

 sections. The length of time in the stains depends upon the 

 material as well as the strength of the stain solution. 



Wherever possible, especially when using combination stains, 

 the course of the operations should be closely watched under 

 the microscope. Differentiation and counterstaining may then 

 be stopped at the critical stage. This is especially important 

 when a second stain tends to reduce the primary one. In such 

 cases, overstain with the first stain and cease the differentiation of 

 it before the correct point has been reached. 



When the differentiation with an aqueous or alcoholic counter- 

 stain is difficult, owing to very great loss of stain, dehydrate the 

 sections to 95 per cent, alcohol and differentiate the primary 

 stain. Then clear with a solution of the counterstain dissolved 

 in clove oil. Crystal (or gentian) violet, erythrosin, light green 

 and orange G may be employed thus. This method of staining, 

 however, appears merely to paint a coat of the dye on the un- 

 stained, non-lignified tissues. The staining is usually brilliant 

 but the differentiation dubious. 



See also Earl, Science, Ixxii, 1930, p. 562 (butyl alcohol 

 procedure). 



650 



