HAEMOSPORIDIA 489 



days; in P. malariae, 4-5 weeks, with the onset of fever lagging 3-12 

 days behind; and in two strains of P. falciparum, one, 6-25 days and 

 the other, 9-13 days; in another observation, P. falciparum was 

 observable in the peripheral blood in 5-9 days and the onset of fever 

 in 7-12 days. 



The paroxysm of malaria is usually divisible into three stages: chill 

 or rigor stage, high temperature or febrile stage (104° F. or over) 

 and sweating or defervescent stage. The time of paroxysm corre- 

 sponds, as was stated already, with the time of liberation of mero- 

 zoites from erythrocytes, and is believed to be due to extrusion of a 

 toxic substance into the blood plasma. The nature of this toxic ma- 

 terial is however unknown at present. In the grown schizonts as well 

 as in gametocytes of Plasmodium, are found invariably yellowish 

 brown to l)lack pigment granules which vary in foi-m, size and num- 

 ber among different species. They are usually called haemozoin gran- 

 ules and are apparently the catabolic products formed within the 

 parasites. They possess certain taxonomic significance. The infected 

 erythrocytes, if stained more or less deeply, may show a punctate 

 appearance. These dots may be small and numerous in the erythro- 

 cytes infected by P. vivax or P. ovale {Schilffner^ s dots) or few and 

 coarse in those infected by P. falciparum, {Maurer's dots). 



The condition w^hich brings about the formation of gametocytes 

 is not known at present. The gametocytes appear in the peripheral 

 blood at various intervals after onset of fever, and remain inactive 

 while in the human blood. The assumption that the macrogameto- 

 cytes undergo parthenogenesis under certain conditions and develop 

 into schizonts as advocated by Grassi, Schaudinn and others, does 

 not seem to be supported by factual evidence. The initiation of 

 further development appears to be correlated with a lower tempera- 

 ture. If living mature microgametocytes of human Plasmodium 

 taken from an infected person are examined microscopically under 

 a sealed cover glass at room temperature (18-22° C), development 

 takes place in a few hours and motile microgametes are produced 

 ("exflagellation"). Similar changes take place W'hen the gameto- 

 cytes are taken into the stomach of mosquitoes belonging to gen- 

 era other than Anopheles, but no sexual fusion l^etween gametes 

 occurs in them and all degenerate sooner or later. In the stomach of 

 an anopheline mosquito, however, the sexual reproduction of human 

 Plasmodium continues, as has been stated before. 



All species are transmitted by adult female mosquitoes. The males 

 are not concerned, since they do not take blood meal. The species of 

 Plasmodium which attack man are transmitted only by the mosqui- 



