PROTOZOA 189 



Mixed infections with the different organisms or with two or 

 more broods of the same organism may occur, so that quotidian 

 and irregular paroxysms may be produced. 



Transmission. Malaria is spread by means of a mosquito, 

 the anopheles, in whose body the protozoon undergoes its 

 highest development. Man is the intermediate host. 



Methods of Examination for Malarial Organisms. 

 i . Fresh preparations are made by placing a small drop of blood 

 on a slide and a cover-glass over it, so that only a thin film is 

 formed. A ring of vaselin is smeared over the edges 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 

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

 cent, phenol. 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 i per 

 cent, aqueous solution of Grlibler's medicinal methylene-blue 

 are mixed, and the resulting precipitate allowed to stand for 

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



Fig. 116. Various forms of malarial parasites (Thayer and Hewetson): 

 i-io Inclusive, tertian organisms; 11-17 .inclusive, quartan organisms; 18-27 

 inclusive, estivo-autumnal organisms. 



i, Young hyaline form; 2, hyaline form with beginning pigmentation; 

 3, pigmented form; 4, full-grown pigmented form; 5, 6, 7, 8, segmenting forms; 

 9, mature pigmented form; 10, flagellate form. 



n, Young hyaline form; 12, 13, pigmented forms; 14, fully developed 

 form; 15, 16, segmenting forms; 17, flagellate form. 



18, 19, 20, Ring-like and cross-like hyaline forms; 21, 22, pigmented 

 forms; 23, 24, segmenting forms; 25, 26, 27, crescents. 



