PLASMODIUM. 275 



Double and triple infections sometimes occur owing to 

 inoculations by mosquitoes on different days. Each group 

 of parasites undergoes schizogony independently, thus attacks 

 of fever occur in cases of single infection every seventy- two 

 hours, that is, on the fourth day (hence quartan). Double 

 infection may cause the attacks to appear on two successive 

 days, and then again on two successive days after an interval 

 of twenty- four hours. In cases of triple infection attacks of 

 fever take place every twenty-four hours. 



Mixed infection of more than one species may also occur. 

 Very often P. vivax and Laverania malaria are found in the 

 same blood-film, as both these species are of commoner 

 occurrence than P. malarise. But the latter may also be met 

 with in association with either of the others, and occasionally 

 all three have been seen in the same blood-film. The diagnosis 

 of these mixed infections will depend upon the finding of 

 undoubted forms of each species. 



Habitat. — Blood of man in almost all parts of India {vide 

 map on p. 279) and in the body of several species of Anopheles, 

 such as A. annularis Van der Wulp, A. culicifacies Giles, 

 A. fluviatilis James {^=A. listoni Liston), A. maculatus Theo., 

 A. minimus Theo., A. philippinensis Ludl., A. stephensi 

 Liston, A. sundaicus Rodenwaldt, and A. varuna Iyengar. 



Distribution of the Human Malarial Parasites. 

 The climatic features of the different part of India being 

 so diverse, greatest diversity of distribution of species of 

 malarial parasites is found in the country. Knowles, Senior 

 White, and Das-Gupta (1930) have come to the following 

 general conclusions on the basis of the available data : — 



(1) In the north-west of India P. vivax tends to predominate 

 during the spring and early summer and L. malarise in the 

 late autumn. P. malarise is quite unimportant. 



(2) The importance of P. malarise becomes greater and 

 greater as one passes from the N.W. Frontier Province to the 

 east and south-east. In brief we may trace two chains of 

 increasing quartan prevalence, as follows : — 



(a) Across Northern India the figures run : 



N.W.F.P., 0-3 per cent. ; Punjab, 1 ; Delhi Province, 

 1-2 ; U.P., 4-6 ; Bengal, 12-3 ; Assam, 9-9 ; Burma, 

 21-2. 



{b) Down the west coast of India : 



Sukkur and Sind, 15-2 per cent. ; Bombay City, 6-6 ; 

 Goa, 9 ; Kanara, 2-1 ; Mysore State, 15-7 ; Coorg, 

 24 ; Ceylon, 33 (in some places up to 71 per cent.). 

 Other hilly areas where the incidence is high are the 

 Central Provinces, 19 per cent., and the Madras Agency 

 Tracts, 41. 



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