162 ESSENTIALS OF BACTERIOLOGY. 



of the cover-glass to prevent evaporation. This is the best 

 method for studying flagellation and fertilization, but is less 

 satisfactory for routine clinical work than 



2. Stained Smears. These are made by spreading a drop of 

 blood in a thin film over one slide with the edge of another, 

 drying in the air, and staining. Many stains have been devised 

 for the malarial organism, but the following are sufficient for 

 ordinary use : 



(1) Marchoux's Thionin Stain. Add 20 c.c. of saturated solu- 

 tion of thionin in 50 per cent, alcohol to 100 c.c. of 2 per cent, 

 carbolic acid. Fix the smears and stain for fifteen to twenty 

 seconds. The malarial organisms are stained a deep purple, 

 strongly contrasting with the faint green of the red cells, so 

 that they are readily recognized. 



(2) Jenner's Stain. This is excellent for routine work, as no 

 preparatory fixation is required. Equal parts of a 1.2 per cent, 

 aqueous solution of Griibler's water-soluble eosin and a 1 per 

 cent, aqueous solution of Griibler's medicinal methylin-blue 

 are mixed and the resulting precipitate allowed to stand for 

 twenty-four hours, washed, and dried. Half a gram of this is 

 dissolved in 100 c.c. of pure methyl-alcohol. The smears are 

 dropped into this stain for one to three minutes, without pre- 

 vious fixation, and at once rinsed in distilled water. The 

 malarial parasites are stained blue, the cell-bodies a reddish 

 brown. 



(3) Wright's Chromatin Stain, This is the best of the chroma- 

 tin stains. For its preparation, which is quite complicated, see 

 Wright, Journal of Medical Research, vol. vii., 1902. It is used 

 as follows : 



1. The stain is poured over the film and allowed to remain 

 for one minute to secure fixation. 



2. Add distilled water drop by drop until a metallic scum is 

 formed on the surface. The staining now takes place and re- 

 quires two to three minutes. Wash in distilled water until a 

 pinkish tint appears in the thin portions of the smear. The 

 body of the malarial parasite is stained blue, and its chromatin 

 a lilac to red color. The red cells are orange pink. 



