

36 W. H. E M I G 



trasts are obtained with Thionine, C. I. No. 920, Methylene Green, 

 C. I. No. 924, or New Methylene Blue, C. I. No. 927. 



258. Sudan IV is insoluble in water but soluble in alcohol, red- 

 dish violet in alkaline solutions; 1/10 gram in 50 ml. of 95 per cent 

 alcohol and 50 ml. of 1 per cent sulfuric acid ; heat to 50° C. From 

 paraffin sections of various tissues the fats and oils are extracted 

 with alcohol and xylene. Those structures which formerly con- 

 tained fats are readily stained with either basic or direct dyes. 



Freehand sections of fresh tissue are placed in Sudan IV at 50° 

 C. for an hour or longer. The tissues containing fats become 

 bright red which is slightly more intense and darker than the color 

 produced by Sudan II, C. I. No. 73, or Sudan III, C. I. No. 248. 

 Tissues consisting of carbohydrates or proteins remain unchanged. 



266. Janus Red B is a basic dye, light 4. Parenchyma be- 

 comes fugitive pink to red depending on the length of time in the 

 stain. 



280. Biebrich Scarlet, Crocein Scarlet 5 R is an acid dye, light 

 3; ^ gram in 100 ml. of distilled water and 1 ml. of 1 per cent sul- 

 furic acid. This is the best red acid dye for staining plant tissues. 

 It is more scarlet and more fast than Azorubine; it may be used in 

 techniques calling for Acid Fuchsine. Tissues fixed in formalin, 

 picric- formalin-acetic, or in Zenker's solution take a brilliant color ; 

 after Gilson's fixative the stain is not always satisfactory. As a 

 rule Biebrich Scarlet does not overstain mature tissues but differen- 

 tiates easily with green, blue, or violet basic dyes. 



Use Biebrich Scarlet on vascular tissues 24 hours and counter- 

 stain with: (1) Methyl Violet, C. I. No. 680, one to three minutes, 

 (2) Victoria Blue B, C. I. No. 729, five minutes, (3) New 

 Methylene Blue, C. I. No. 927, five minutes, or (4) Aldehyde 

 Green, C. I. No. 676a, five minutes for a mixture of red, green, and 

 greenish black. 



Except for certain invertebrates Biebrich Scarlet is not so good 

 on animal tissues. On whole mounts of small animals use a mix- 

 ture of ten parts Sun Yellow, C. I. No. 620, and two parts Biebrich 

 Scarlet for five minutes ; follow with Niagara Sky Blue, C. I. No. 

 520, for 15 to 30 seconds. 



