PERIODICITY IN MALARIA 



401 



selves (not their deviations, as is ordinarily used), n, the number 

 of parasites drawn and AP, the square of the mean. 



1000 



2. The coefficient of variation is derived from the formula 



M 



in which represents the standard deviation, and M, the mean. 

 These data will indicate the sharpness of the periodicity. For ex- 

 ample, if the cycle is fairly synchronous, the coefficient of varia- 



12 



H 





C£? 



25 



JL 



Percentage of Sma/! Fbms- 

 Coefffcient of Variation — 



^ -o- 



-^ 



/■ 



,V 

 // 



/r 

 // 



V-'^ 



/ ; 



\ 



..<^ 



-| 1 



Hour of 



I 



Fig. 27. — Graph showing percentage distribution of small forms and coeffi- 

 cient of variation for all forms during one period of sporulation in Bird 40. 

 (From L. G. Taliaferro, 1925.) 



tion will be low at all times (there will be little variation in size), 

 except at sporulation time (when there will be both large and 

 small forms). 



Applications of these methods based on changes in size have 

 brought out some interesting facts in avian malaria. The present 

 author (1925) has found that in one strain, Plasmodium cathe- 

 merium Hartman, 19276 (=P. prcecox or relictum of earlier 



