Appendix B: Some Standard Reagents and Their Uses 171 



mold. Alum cochineal is one of the best stains for entire objects. 

 It is easy to work with, and does not overstain. The time required 

 for staining is from 24 to 36 hours ordinarily. After staining, 

 the object should be washed in water for 15 or 20 minutes to 

 extract the alum, which would otherwise crystallize when the 

 object is placed in alcohol. Too long an immersion in water may 

 extract the stain to too great an extent. From water the object 

 should be passed upward through the grades of alcohol, remaining 

 about an hour in each. The writer has found alum cochineal 

 especially valuable for flatworms (tapeworms, flukes, etc.) and 

 embryos. If it is desired to use a counterstain with it, Lyon's 

 blue, picric acid, orange G, or light green will answer. 



28. Alum Carmine. 



Powdered carmine 1 gram 



Ammonia alum (2.5 per cent, aqueous solution) 100 c.c. 



Boil for 20 minutes, and filter when cool. The uses and 

 manipulation are the same as for 27. These stains affect calcareous 

 structures injuriously. 



29. Anilm Stains. Read the general remarks about anilin 

 stains in chap. ii. The formulae for some of the most important 

 are given separately in this list in their proper alphabetical 

 position. 



The dyes are dissolved in water, in alcohol of any desired 

 strength, or in anilin water, according as they are soluble in these 

 media, or as they meet the needs of the operator. Some workers 

 even use some of them as counterstains dissolved in the clearing 

 fluid. For the study of nuclei, after Hermann's or Flemming's 

 fluid has been used for fixing, the writer has found a weakly 

 alcoholic anilin water solution to be the most satisfactory. As 

 cytoplasmic contrast stains, alcoholic solutions (in 70 to 95 per 

 cent, alcohol) have given the best results. Anilin water is made 

 by shaking up 4 c.c. of anilin oil in 90 c.c. of distilled water and 

 filtering the mixture through a wet filter. Enough alcohol may 

 be added to make it a 20 per cent, alcohol, if a weakly alcoholic 

 solution is desired. 



The length of time which sections should be immersed in the 



