250 GUIDANCE IN MAKING PERMANENT PREPARATIONS 



back through 50 per cent and 35 per cent alcohol to water, 

 to which a few drops of hematoxylin has been added, or put 

 from water into alum carmine. The former stain, if dense, 

 should not require over twenty to thirty minutes, but objects 

 must be left in alum carmine ten to twenty hours. When a 

 good color is obtained, run the material through the grades 

 of alcohol, from the lowest to the highest (five minutes in 

 each), and mount as in the case of the borax carmine objects. 

 Objects stained in alum carmine will probably not over- 

 stain; but excess of hematoxylin should be extracted with 

 acidulated alcohol when the 70 per cent grade is reached, 

 after which it is very essential that all of the acid be re- 

 moved by repeated changes of 70 per cent alcohol. Other- 

 wise the objects will fade. 



