34 NUCLEAR STAINS. 



by Ammonia, Soda, or Lithia ; but as the neutral picrates of 

 these alkalies have in themselves no staining power, and the 

 manner in which the Picric Acid is combined has never been 

 accurately determined, no scientific explanation of their 

 action can be given. 



The following formula and method is that generally recom- 

 mended, and in a large number of comparative experiments 

 was found to give the best results. 



(1.) AMMONIA FICIIO CARMINE. 



Carmine, 1 grm. ; Strong Solution of Ammonia, 3 cc. ; 

 Distilled Water, 5 cc. Dissolve the Carmine in the Ammonia 

 and Water with a gentle heat, then add Saturated Aqueous 

 Solution of Picric Acid, 200 cc. ; heat to boiling and filter. 

 This solution gives good results when used as follows : 

 Take a section which has been rinsed in Distilled Water and 

 lay it out flat on a glass slide, drain off the superfluous water, 

 then pour on to the section several drops of the Picro-Carmine 

 Solution, warm the slide over a spirit lamp to a heat that can 

 be borne by the hand when touched with the glass (if the 

 section be too strongly heated it will shrivel), keep it about 

 this temperature for 5 or 10 minutes, remove the excess of 

 stain by tilting the glass and wiping it with a cloth or filter 

 paper, leaving some of the stain in the section, then place 

 one or two drops of Formic Farrant (p. 85) upon the section 

 and apply the cover-glass. The staining of the section is 

 much improved after it has been mounted 2 or 3 days and 

 exposed to daylight. 



A section of skin gives the most striking results by this 

 method. Nuclei and the transverse muscular fibres stain 

 red, the remainder yellow. 



The following formula for Eanvier's Picro-Carmine, pub- 

 lished in " Lee's Microtomists' Vade Mecum," 1890, p. 82, was 



