On Staining. 33 



in utility while it surpasses it in beauty ; it is not quite 

 so easily fixed, otherwise it can be used in the same 

 manner and as readily as rosein. It has this advan- 

 tage over rosein, it is a much softer colour to the eye 

 and makes a really beautiful combination with some of 

 the aqueous solutions in double staining. 



It is readily soluble in spirit, and even diluted makes 

 a very opaque solution, rendering it a matter of diffi- 

 culty to find the sections in it ; they may be seen, how- 

 ever, by holding the watch glass against a lamp or 

 bright sky. 



Good results are often obtained with this colour by 

 removing sections from water and letting them spread 

 out a little on the needle in a strong solution and 

 then removing them quickly to an aqueous solution of 

 another color. 



21. Citranine. A yellow substance insoluble in water 

 and only soluble in spirit by the application of heat. 

 It does not seem to give a deep enough colour to be a 

 useful staining agent in microscopical investigations, 

 but a more extended trial may bring out some valuable 

 peculiarities, as it seems to differ a good deal from the 

 other anilins. 



22. Aurine. This is another colour of which there 

 is not much known of its action on animal tissues ; as 

 far as it has been used, it has not given any satisfactory 

 result. 



23. Pure Opal Blue. This is the best blue soluble in 

 spirit, and is therefore useful in cases where an aqueous 

 stain is not admissible. It is made by dissolving the 

 powder in spirit and then filtering it. Methylated 



