IOO 



THE ANIMAL PARASITES OF MAN 



merit. It may be assumed that they are transformed directly 

 into the amoeboid form of the Hsemosporidia, and multiply by 

 schizogony until their number is sufficiently great to produce the 

 first paroxysm of fever. If a small number only happen to be 

 present in the salivary glands of the mosquito they are all dis- 

 charged with its first bite ; in other cases only a few are got rid 

 of, so that under these circumstances one single Anopheles is 

 capable of infecting several persons. The same mosquito also 

 may repeatedly take up malarial plasmodia from sick persons, and 

 thus may harbour simultaneously different stages of development, 

 and thus repeatedly replenish its salivary glands with sporozoites. 



FIG. 44. Section through a tubule of the. sail vary gland of an Anopheles, with sporo- 

 zoits of the pernicious parasites ; above an isolated sporozoit with higher magnification. 

 (After Grassi.) 



Research has demonstrated that : THE MALARIAL PARASITES OF 



MAN UNDERGO AN ALTERNATION OF GENERATIONS AND REQUIRE 

 TWO DIFFERENT HOSTS FOR THEIR COMPLETE DEVELOPMENT ; the 



asexual development (SCHIZOGONY) takes place in. the blood of 

 man, the sexual development (SPOROGONY) in the body of species 

 of the genus Anopheles. The transmission to man is effected exclu- 

 sively by the bite of Anophelinae, which harbour in their salivary 

 glands the mature sporozoites of the various plasmodia : the infec- 



