On Staining. 27 



delicate color when used alone and almost too trans- 

 parent, but in combination it becomes opaque. 



This is the ordinary eosin, there is also an alcoholic 

 eosin called primrose which is much used by silk dyers, 

 it is soluble in a weak solution of spirit of wine, it fixes 

 readily and gives a more brilliant color than ordinary 

 eosin, and is not affected by light. There is also a blue 

 shade of eosin which is said to have a great affinity for 

 wool, and can be fixed readily by a solution of soda 

 hypophosphis ; this might be useful for investigations 

 in diseases of the hair. 



7. Picro- Carmine. This useful stain is difficult to 

 make and the process is very tedious, it is better there- 

 fore to buy it prepared for use. It can be procured 

 from Martindale, New Cavendish Street, at a reason- 

 able price. 



Filter about 10 drops into a watch-glass and dilute 

 with distilled water. The sections must remain for 

 some time, from twenty minutes to half an hour, and 

 if at the end of that time they have not stained suffi- 

 ciently, a little more picro-carmine may be added. 



They are then placed in water acidulated with a few 

 drops of acetic or picric acid and left for an hour. 



When making experiments in treble staining a num- 

 ber of sections may be stained in picro-carmine and 

 then placed in methylated spirit ; there they may re- 

 main until required, as the spirit does not affect the 

 stain, which forms a very good ground color, on which 

 to try combinations of different anilines. 



It is also a good stain for fresh tissues, such as 

 mesentery when used with logwood. Also in sections of 



