52 PARASITIC AMGEBJE OF MAN. 



add 1 gm. of methylene blue (Grubler) ; heat the 

 mixture for one hour in an Arnold sterilizer or other 

 steam sterilizer, after the steam is up. After heating 

 allow the solution to cool. Make a 1 to 1,000 

 solution of yellow aqueous eosin (Grubler) and add 

 this, while stirring, to the cooled methylene blue solu- 

 tion, in about the proportion of 500 c.c. of the eosin 

 solution to 75 c.c. of the methylene blue solution. 

 This should be done in a white dish of some kind, in 

 order that the precipitate that forms as the eosin 

 solution is added may be easily seen. The proportion 

 of eosin solution added to the methylene blue solution 

 will vary in different batches of the stain, but the 

 eosin solution should always be added until a well- 

 marked precipitate follows after stirring. A marked 

 metallic scum will appear upon the surface of the 

 mixture at the time the eosin solution is in sufficient 

 quantity and this may be used as an indicator, but 

 if no precipitate is present when the metallic scum 

 appears the eosin solution should be added until it 

 appears. The mixture should then be allowed to 

 stand for fifteen or twenty minutes, and then filtered 

 through one small filter-paper, the precipitate saved, 

 dried in a hot-air oven, removed from the filter-paper, 

 and used in making the staining solution. The 

 precipitate, which is a fine powder, greenish in color, 

 will keep well and can be used as stock material for 

 months. 



