999 



DISEASES DUE TO PROTOZOA 



propagation of mosquitoes. It is not communicable 

 by contact of man to man. It is the infestation of 

 the red blood cells by a parasite having three forms, 

 belonging to the order Hemosporidia. The parasites 

 are called the Plasmodium vivax, the P. malarioe, and 

 the P. falciparum. Three types of attack corre- 

 spond to the three protozoal species: (1) That which 

 gives chills and fever every third day, the tertian 

 malaria; (2) one where the paroxysm appears every 



FIG. 64. Some of the principal forms assumed by the plasmo- 

 dium of tertian fever in the course of its cycle of development. (After 

 Thayer and Hewetson.) 



fourth day, the quartan type; and (3) a continuous, 

 typhoid-like type, the malignant or estivo-autumnal 

 fever. 



The species vary in finer morphological details, but 

 they follow the same course in their transmission 

 and development in regard to infectivity, except that 

 they require differing times for their full development. 



The female mosquitoes of the genus Anopheles carry 

 the disease from one person to another. They fly and 

 bite in the early evening. These mosquitoes may be 



