274 APPLIED BACTERIOLOGY 



1. The parasite may be found in every case of malaria. 



2. It is only found in malaria. 



3. It accounts for a peculiar feature of malaria, i.e., 



melansemia. 



4. The cycle of the parasites corresponds with the cycle 



of malarial fever. 



5. Quinine kills the fever-causing phase of the parasite 



and cures the fever. The crescent form of the 

 parasite which is not pyrogenetic, is not influenced 

 by quinine. 



6. Malarial fever can be conveyed by injections of blood 



containing the parasite, and the parasite subse- 

 quently appears in the blood of the individual so 

 inoculated. 

 As our knowledge of these remarkable organisms is as 

 yet very far from complete, and as there are considerable 

 differences of opinion on several important points, we shall 

 do no more than touch on the life-history of the parasite. 



Malaria is endemic in certain localities, which are most 

 often situated in hot climates, and they are usually, though 

 not necessarily, low-lying and swampy. Moisture of the 

 upper layers of the soil is an almost invariable condition in 

 malarious districts. The tendency to malaria increases 

 with the temperature, especially if the diurnal range is 

 high. Clay soils are the worst, but chalk and sandy soils 

 may become highly malarious if from any cause the ground 

 water is high. 



The malarial diseases reach their maximum of frequency 

 and intensity in tropical and sub-tropical localities. They 

 continue to be endemic for some distance into the tem- 

 perate zone, but with diminishing severity and frequency 

 as the higher latitudes are reached. As the intensity of 

 the endemic or epidemic prevalence diminishes, individual 

 cases assume more and more the intermittent type. 



