PLASMODIA 297 



pigmented mononuclear leukocytes has been taken as evidence of 

 malaria by some workers, even though no parasites could be found 

 in the blood. A striking feature in estivo-autumnal fever is the 

 presence of enormous numbers of infected red blood cells in the 

 capillaries of the brain and abdominal viscera. 



Immunity. Many mild cases recover without treatment 

 hence it is evident that some immunity is produced by an infection. 

 It is temporary, however, and does not protect against reinfection. 



Prophylaxis. Since malarial infection is transferred only by 

 a certain species of mosquito a malarial patient can be considered 

 a source of danger only when that particular variety of mosquito 

 is in the vicinity. Conversely, the Anopheles mosquitoes are harm- 

 less if they have never had the opportunity of drinking blood 

 containing gametocytes from a malarial patient. With the 

 knowledge of the manner in which infection is spread active 

 measures have been taken in different countries to control the 

 disease, the most efficacious of which is the extirpation of the mos- 

 quitoes by the suppression of their breeding places. Since Anoph- 

 eles breeds in open ponds and natural collections of water in 

 fields and swamps this may be accomplished by filling up low places 

 and drying the surface of land with drains. Where drainage is 

 not practical the number of mosquitoes may be kept in check by 

 introducing fish into ponds and other collections of water. Upon 

 limited surfaces the larva may be destroyed by cutting off the air 

 supply by means of a thin layer of coal oil. 



Koch advocated the administration of quinine in order to destroy 

 the parasite within the human body and thus prevent the infec- 

 tion of the mosquito. The drug has a remarkable effect upon 

 the merozoites of the tertian and quartan types and great success 

 has resulted from its use. A single large dose may be administered 

 as the temperature begins to decline, that is, shortly after the 

 young merozoites have been liberated into the blood stream ; or in 

 cases of double or triple infection where different broods come to 

 maturity at different times smaller doses at definite intervals 

 have given better results. Unfortunately, the gametocytes are 

 quite resistant to the drug. 



