WILLIAM H. TALIAFERRO 



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After the incubation period the asexual stages of the parasites are to be found in the 

 peripheral blood in varying numbers during the entire course of the infection and undergo 

 their C3'cle of development and reproduction at the same rate throughout. From the very 

 beginning, only a number of the merozoites are viable; this probably represents a natural 

 resistance of the host. During the first part of the infection relatively few parasites are killed, 

 so that they accumulate in the blood and give rise to the acute stage of the infection. Sooner 



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Fig. 9. — Graph illustrating the t>TDe of number curve usually encountered in the course of an 

 infection of P. praecox in the canary. 



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Fig. 10.— Graph showing the changes in mean size of the asexual forms and the number curve 

 through the acute period and crisis in an infection with P. praecox in a canary. The uniform rate of 

 reproduction (as shown by the regularity in the mean-size curve) and the type of number curve (as 

 seen in the preceding figure) indicate that there is a parasiticidal but no reproduction-inhibiting 

 resistance developed. (From data by L. G. Taliaferro.) 



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