DISEASES CAUSED BY PROTOZOA. 
123 
Malarial Fever. 
Malarial fever is an acute infection caused by a 
protozoan parasite. It is characterized by intermit¬ 
tent chills and fever and sweats, and accompanied by 
anemia. There are three types of the fever caused by 
three species of the parasite: the tertian type, with 
chill and fever every third day; the quartan, with 
Fig. 19.—Plasmodium vivax, parasite of tertian fever. In the 
upper row and on left of lower row, various stages of intra- 
corpuscular development; the two last figures in lower row are 
free sexual individuals, microgametocytes (sperm cells), which 
are about to set free the microgametes, or males. (After 
Reinhardt.) 
chill and fever every fourth day; and the estivo- 
autumnal, with an irregular fever like typhoid. 
The disease is transmitted from one person 
to another by the female mosquito of the genus 
Anopheles. They can be distinguished from the ordi¬ 
nary mosquito, the Culex, by their position when they 
alight. The body of the Culex is always parallel to 
the surface, while the body of the Anopheles forms a 
sharp angle with it. When the Anopheles feeds on 
