Phylum Protozoa 367 



aware of the fact that certain sections were dangerous ones in which 

 to Hve. The "night airs" still have a bad reputation among many 

 peoples. At present, we have gone a long way in our knowledge of 

 control measures. At times, it often suffices to destroy the larvae 

 of the mosquitoes by spraying oil over ponds or draining swamps. In 

 tropical areas where the number of breeding places is infinitely more 

 numerous, the problem is much greater. Often the clearing of an area 

 around a town will help as the mosquitoes apparently do not fly very 

 far. Also screening of windows and doors is of some aid. 



A knowledge of the habits of the malaria-carrying mosquitoes often 

 helps in avoiding infection. For example, it is well known that in most 

 areas the mosquitoes fly at sundown and just before dawn. By staying 

 within protected areas at those times, one achieves some degree of pro- 

 tection. Unfortunately, however, the flying habits of the mosquitoes 

 vary from area to area and this is not always too safe a measure. 

 Healthy persons in infected areas often can avoid malaria by taking 

 preventive doses of antimalarial compounds. There are many different 

 drugs at present, including quinine, Atabrine, and Paludrine. These act 

 by killing the sporozoites before they have an opportunity to become 

 established in the blood. After malaria is once acquired, these same 

 drugs are often used to destroy the merozoites. 



Another interesting haemosporidium is Babesia higemina, the 

 causative organism of Texas cattle fever. The life history of this form 

 is somewhat similar to that of the malaria organism with the inter- 

 mediate host being a tick, Margaropus annulatiis. The asexual stages 

 are in the cattle and the sexual stages in the tick. Within the tick, 

 the sexual stages occur in the gut. The zygote migrates from this 

 area into the ova of the tick. As the embryonic ticks develop, the 

 sporozoites get into the salivary glands. After the tick hatches, it may 

 feed on cattle and inject the sporozoites. Control measures consist 

 of destroying the ticks by dipping the cattle and by alternating pastures. 



THE CLASS CILIATA 



The possession of cilia over the body surface distinguishes the 

 members of this class from the rest of the protozoans. Since numerous 

 genera and species are usually present in any hay infusion culture, they 

 often are known as the injusorians. The individuals of this class have 

 developed more complicated organelles than those of any other protozoan 

 class. 



