PROTOZOA 141 



by a flagellate. There are several species which live in the 

 alimentary canal of man and other animals. 



CLASS III. SPOROZOA 



This group of protozoans contains only species which are 

 entirely parasitic, and they may live in representatives of 

 any phylum of the animal kingdom. There are some which 

 even dwell in the bodies of other protozoans. As would be 

 expected from their parasitic habits, many sporozoans 

 cause diseases in the animals they inhabit. The sporozoan 

 disease of most interest to man is malarial fever, prevalent 

 in all the warm regions of the earth. 



1. Day 



Fever day 

 2. Day 



3. Day 



Fever e/atf 

 4. Day 



\ 



\ 



I 



\ 



A B C D A( B' C' D' /I" 



FIG. 63. A temperature chart of a man sick with malarial fever, and (below) 

 red blood corpuscles containing the parasites causing the disease. Note that 

 there is high fever when an infected corpuscle ruptures, thus freeing spores, 

 poison, and black pigment. A, A', A", young Plasmodium in corpuscle; B, B', 

 well grown; C, C', nearly mature; D, D', ripe spores escaping. 



Malaria is caused by parasites of the genus Plasmodium 

 and there are three different species which cause character- 

 istic fevers. Plasmodium vivax causes " benign tertian 

 malaria" (i.e., mild malarial fever in which there is fever 

 every third day). This parasite can enter a man only when 

 a certain mosquito bearing the disease bites him, and it then 

 migrates from the insect's proboscis directly into the blood. 

 Once in the blood it enters a red corpuscle and grows for 



