PERIODICITY IN MALARIA 405 



laria) merozoites ^ is indepenent of the number of parasites de- 

 stroyed. Thus, the rate of reproduction was found to be constant 

 in B. cathemeriiim, since the cycle took twenty-four hours through- 

 out the acute, crisis, chronic and relapse periods (in fact, whenever 

 parasites could be found in the blood), whereas the number of 

 parasites decreased remarkably at the crisis and subsequently. (See 

 Fig. 26 for data during the acute and beginning of chronic periods.) 

 Hence, it could be concluded that the bird develops, in the course 

 of its infection, a parasiticidal resistance but no resistance affecting 

 the rate of reproduction of the parasites. 



The second method, which has been fully described by Boyd 

 (1929), consists in making blood smears every two or four hours 

 through the day and night, staining them with MacNeal's tetra- 

 chrome stain, and in determining the percentage of sporulating 

 forms to the total parasite population. The method is discussed in 

 more detail in Chapter XXXIX. 



'The number of new merozoites produced is constant for the various 

 stages in the infection (L. G. Taliaferro, 1925). 



