204 ESSENTIALS OF BACTERIOLOGY 



(2) Wright's Chromatin Stain. This is the best of the 

 chromatin stains. For its preparation, which is quite com- 

 plicated, see Wright, Journal of Medical Research, vol. vii, 

 1902. It can be purchased already made. 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 

 requires two to three minutes. Wash in distilled water until 



Fig. 102. Pure culture of trypanosomes of mosquitos Crithidia 

 fasciculata. Multiplication roset showing large and small cells. Nine- 

 day culture (Gen. i X 1500) (Novy, MacNeal, and Torrey). 



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. 



If possible, examinations for malarial organisms should 

 always be made before quinin is administered. 



Trypanosomata. Trypanosomes are flagellate protozoa 

 found in the blood of various animals, and causing a number 

 of diseases, such as surra, dourine, and nagana, affecting 

 horses and cattle, especially in tropical countries, and causing 



