SCHARLACH 505 



dye in 70 per cent, alcohol. The sections are transferred from water to 

 the stain, which has been freshly filtered into a tightly closing vessel. 

 Evaporation of the alcohol causes a precipitation of the staining material. 

 Wash in water, stain the nuclei lightly with alum haematoxylin, and 

 mount in glycerin. Fat and lipoids stain red. 



Nile Blue. Frozen sections of fresh material or material fixed in 

 formalin for not more than 12 hours are stained for 15 minutes to 2 hours 

 in a saturated aqueous solution of nile blue (Griibler). Wash in distilled 

 water for 5 minutes or more, and transfer to tap water. If after 5 minutes 

 in the tap water the section does not assume a reddish hue, add a small 

 amount of alkali to the tap water. When the section is reddish, transfer 

 to distilled water. Mount in glycerin or glycerin jelly and examine at once. 

 Neutral fat red; lipoids blue. 



Osmic Acid. Fat and myelin in fresh tissues may be blackened in a 

 i per cent, aqueous solution of osmic acid. The myelin sheaths of teased 

 nerve fibers may be so treated, the fragments dehydrated, cleared in chloro- 

 form, and mounted in chloroform damar. Sections may be prepared from 

 tissues fixed in Marchi's fluid (p. 491), showing the fat blackened by the 

 osmium. Use chloroform to remove paraffin from the sections, and 

 mount in chloroform damar. 



Wright's Blood Stain. After 0.5 gm. of sodium bicarbonate has been 

 completely dissolved in 100 c.c. of distilled water, add i gm. of Griibler's 

 methylene blue (either the form called BX, Koch's, or Ehrlich's rectified). 

 "The mixture is next to be steamed in an ordinary steam sterilizer at 

 100 C. for i hour, counting the time after steam is up. The heating 

 should not be done in a pressure sterilizer, or in a water bath, or in any 

 other way than as stated." The mixture is then removed from the steri- 

 lizer and allowed to cool, the flask being placed in cold water if desired. 

 When cold, it is poured into a large dish or flask. Add to each 100 c.c. 

 of the methylene blue solution, stirring or shaking meanwhile, about 

 500 c.c. of a o.i per cent, solution of Griibler's yellowish eosin soluble in 

 water. The eosin solution should be added until the mixture, losing its 

 blue color, becomes purple, and a scum with yellowish metallic luster forms 

 on the surface, "while on close inspection a finely granular black precipi- 

 tate appears in suspension." The solution is then filtered and the pre- 

 cipitate allowed to become perfectly dry on the filter paper. The stain 

 is made by dissolving 0.3 gm. of the precipitate in 100 c.c. of pure methyl 

 alcohol. The stain need not be filtered, and like the precipitate, it keeps 

 indefinitely. If by evaporation of the alcohol it becomes too concentrated, 

 as shown by the formation of a precipitate when it is used, it should be 

 filtered and a small quantity of methyl alcohol added. 



Blood is obtained usually from a needle puncture in the lobule of the 

 ear. A drop of blood is caught in the center of a perfectly clean dry 



