38 Pier o- carmine and Anilin Colours. 



thoroughly removed, place the sections in a little of No. 

 3 solution undiluted, and let them remain in it until 

 they show a distinct blue tinge : the proper depth of 

 this staining will be learnt by practice. 



When carefully used this staining process is an ad- 

 mirable one, but there are one or two points that 

 have to be attended to, or the two colours will not 

 be sufficiently differentiated. If the section is left 

 too long in the acid mixture the carmine will be 

 taken out of the edges and these parts will after- 

 wards take on the blue stain deeply, and so give a 

 result the very opposite of that intended, as the 

 whole value of double staining depends on one co- 

 lour picking out the whole of one particular tissue 

 throughout the section, and if this is not done the spe- 

 cimen is of no use. If the carmine stain is only just 

 sufficiently acted on by the acid, so as to change the 

 original dull purple colour to a bright rose, and the 

 edges of the specimen are not bleached, it will, when 

 put in the indigo -carmine solution, stain evenly through- 

 out. 



If the acid solution be too strong it will have the 

 same effect as too long immersion in a weaker solu- 

 tion, and a few seconds will bleach the edges. This 

 process will be found very useful in pathological inves- 

 tigation, as the carmine picks out very distinctly all the 

 new growths. 



PlCRO-CAKMINE AND ANILIN COLOUES. 



Some very good results may be obtained by staining 

 sections first in pier o- carmine, then letting them remain 



