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RESEARCH IN PROTOZOOLOGY 



ture and dryness of a room, as well as that of an incubator, 

 vary so much in different laboratories that it is impossible to 

 give precise rules for drying, but a very little experience will 

 guide. 



Staining. It is essential to use a good quality of Giemsa stain. 

 The water used for diluting it must be neutral, or only slightly 

 alkaline, and must be nearly, or quite, free from salts. 



Fig. 20. — A, Slide-box held against supporting wooden blocks. B, Block of 

 slides, with group label, in staining-dish. 



The stock Giemsa solution may be made up by the following 

 formula: Dissolve Azur II eosin, 0.3 gram, and Azur II, 0.08 

 gram, in twenty-five cubic centimeters of pure anhydrous gly- 

 cerin at 60° C. Then add twenty-five cubic centimeters of ab- 

 solute methyl alcohol (C.P., acetone-free) at the same tempera- 

 ture. Allow the glycerin-methyl alcohol solution to stand over- 

 night and then filter. 



The Azur II may be omitted from the formula of a Giemsa 

 solution to be used for thick films. According to Giemsa (Centralbl. 

 f. Baktcriol. I Abth. Orig., 1924, Vol. 91, No. 5, pp. 343-346) a 

 glycerin suitable for this stain should have a specific gravity of 

 1.26 and a water content of only 1.5%. 



In recent years we have been using a Giemsa solution ready pre- 

 pared. We prefer Azur eosin, Gruebler. (This stain may be ob- 

 tained in America of the American Kreuger & Toll Corp., New 

 York, under the name of "Azur Eosine Solution for Romanowsky 

 Giemsa Staining." An excellent Giemsa solution can also be 



