SPECIFIC STAINS. 43- 



SPECIFIC STAINS. 



These may be defined as stains which, possess a peculiar 

 affinity for certain elements in the tissues. The more impor- 

 tant are Osmic Acid, Chloride of Gold, Nitrate of Silver, Vic- 

 toria Blue, Dahlia Violet, Methyl Violet, Iodine, Safranine, 

 Eose Bengale, Nigrosine, Acid Fuchsine, and Congo Eed. 



OSMIC ACID. 



Aqueous solution, 1 p. c. (see also p. 8). 



To be kept in an opaque bottle, and away from the light. 



Useful for staining fatty elements, medullated nerve fibre, 

 and elastic fibres. It is especially valuable for demonstrating 

 fatty degeneration of organs. 



Very small pieces of tissue in the fresh state are stained 

 and fixed at the same time. It is also used in combination 

 with Chromic Acid, as in Flemming's and Fol's solutions. 



Material for sections should be hardened in Miiller's Fluid, 

 and cut on the freezing microtome. Alcohol partially dissolves 

 the fat, and is, therefore, unsuited for the hardening, except 

 when this is of no consequence. Osmic Acid also stains any 

 fat which is left after treatment with Alcohol. 



Sections are placed for 6 to 12 hours in J to iVp- c - solution, 

 carefully protected from the light, or for J to \ hour in 1 p. c. 

 solution ; washed in Distilled Water, and mounted in Farrant 

 or Glycerine. 



CHLORIDE OF GOLD. 



\ or 1 p. c. solution in Distilled Water. 



Commercial Chloride of gold is not the pure Chloride AuCls, but the 

 crystallized double Chloride of Gold and Sodium, containing 50 p. o. of 

 Metallic Gold. 



Commercial Chloride of Gold and Sodium is the above crystallized 

 double Chloride mixed with an equal weight of Chloride of Sodium, and 

 contains 25 p. c. of Metallic Gold. 



