EXAMINATION OF BACTERIA WITH THE MICROSCOPE. 43 



Nuclear stains, which may be used as contrast-stains for 

 sections : 



Delapield's Hematoxylin. 



Hematoxylin crystals 4 grams. 



Alcohol 25 c.c. 



Ammonia alum 50 grams. 



Water 400 c.c. 



Glycerin 100 c.c. 



Methyl-alcohol 100 c.c. 



Dissolve the hematoxylin in the alcohol, and the ammonia 

 alum in the water. Mix the two solutions. Let the mixture 

 stand four or five days uncovered; it should have become a deep 

 purple. Filter and add the glycerin and the methyl-alcohol. 

 After it has become dark enough, filter again. Keep it a 

 month or longer before using; the solution improves with age. 

 At the time of using, filter and dilute with water as desired. 



LlTHIUM-CAEMINE (OrTh). 



Carmine 2.5 grams. 



Saturated watery solution of lithium carbonate 100.0 c.c. 



Add a few crystals of thymol. The carmine dissolves readily 

 in the lithium carbonate solution. Filter the stain at the time 

 of using. Sections are to be left in the stain five to twenty 

 minutes. 



Sections stained in carmine are placed directly in acid alcohol 

 (i part hydrochloric acid, loo parts 70 per cent, alcohol) for 

 five to ten minutes. They acquire a brilliant scarlet color. 

 When used as a contrast-stain for tissues containing bacteria, 

 it is best to use it before staining the bacteria, which might be 

 decolorized by the acid alcohol. 



Staining of Blood-films. — The method of Wright is the 

 one recommended. It is appHcable to bacteria and to the 

 parasite of malaria, and is useful as a general stain for blood. 



