PLASMODIUM VIVAX 



573 



they invade fresh corpuscles, and either directly or indirectly are 

 responsible for the chill, fever, prostration, etc. 



The parasites of malaria have a double cycle of reproduction. 

 Asexual reproduction (Schizogony) by spore formation (merozoites) 

 occurs in the blood of man or monkeys; the sexual cycle of repro- 

 duction by copula formation of sexually differentiated gametes occurs 

 in the body of the intermediate host, the mosquito of the genus 

 anopheles. 



Plasmodium Vivax. This is the cause of tertian malarial fever. 

 After its entrance into the body of man it is first seen in the interior 

 of red blood corpuscles as a small, quite motile, hyaline body, variable 



FIG. 200 



Anopheles maculipennis: adult male at left, female at right. (Howard.) 



in shape on account of the contractility and ameboid motion of 

 its protoplasm. After a time the latter contains reddish-brown, 

 rather fine, diffusely distributed pigment, which increases in amount. 

 While the perfectly hyaline bodies are difficult to see under the 

 microscope the parasites are easily visible after they have formed 

 pigment, particularly as the granules in fresh blood are in constant 

 motion in consequence of protoplasmic contractility and currents. 

 About forty-eight hours after its first entrance into the red blood 

 corpuscle the plasmodium has reached a large size, and now fills the 

 enlarged erythrocyte almost completely. The parasite now has lost 

 its ameboid motion, is round in shape, and divides by segmentation 

 into twelve to twenty-four merozoites (asexually produced spores). 



