On Staining. 25 



tissues much better while it has not the deleterious 

 effect of carmine on the eyes when used with lamp 

 light. 



Carmine is, however, valuable in double staining, 

 either as a carmine solution or in conjunction with 

 picric acid as picro- carmine. 



The carmine solution is prepared by mixing : 



Carmine, 3 ss. 

 Borax, 3 ij. 

 Aqua, ^ iv. 



and pouring off the clear supernatant fluid. It must 

 not be filtered. 



3. Indigo- Carmine or Sulphindigotate of Soda. This 

 is a useful stain in conjunction with carmine, especially 

 for pathological specimens. 



First make a saturated solution of the powder in dis- 

 tilled water and filter, take some of this solution and 

 pour it into methylated spirit until it has attained a 

 moderately deep color ; a good deal of the colouring 

 matter will be precipitated, and it must be carefully 

 filtered to remove this, it is then ready for use. The 

 solution should not have a very deep blue color and 

 when held to the light, should show a purplish tint. It 

 does not require long to stain the sections in it, and 

 they should be allowed to remain long enough to stain 

 them evenly, as it will be found that they stain first at 

 the edges, after having been passed through dilute hy- 

 drochloric acid. 



4. Purpurine. True purpurine is a red colouring 

 matter extracted from madder, it is rather expensive 



