HIS PATHOGENIC PROTOZOA 



rapidly and soon escapes from its host cell and conies to lie in the 

 outer layers of the stomach wall, and as it grows projects into the 

 body cavity of the mosquito. The nucleus divides repeatedly, always 

 accompanied by some of the cytoplasm, forming numerous sporo- 

 blasts, and these, in turn, subdivide into innumerable sporozoites; 

 these last escape, with the rupture of the oocyst, into the body 

 cavity. From there they pass to all parts of the mosquito, but 

 especially, perhaps because of chemotaxis, to the salivary glands 

 and ducts, and when next the mosquito bites a warm-blooded host 

 the sporozoites enter the blood stream and start life anew. 



Cultivation of the Malarial Parasites in Vitro. Bass and Johns in 

 1911 announced the cultivation of a few generations of plasmodium 

 vivax in vitro under strict anaerobic conditions. Ten c.c. or more of 

 blood from a malarial patient is defibrinated and distributed in small 

 test tubes in one c.c. quantities and to it is added one per cent of a 

 fifty per cent solution of glucose. The red cells settle so that they 

 are covered with one-half cm. of serum; the parasites grow in a 

 thin layer near the top of the cell mass; beneath this they die, or 

 are phagocyted. The optimum temperature is 19 to 40 C. 



Bass states that he has cultivated all three species of plasmodia 

 by destroying the complement by heating one-quarter to one-half 

 hour at 40 C. Under strict anaerobiasis it was possible to transfer 

 the cultures and to keep them alive for twenty days. 



Transmission. Transmission is solely by various species of 

 anopheles mosquitoes. Although there are fifty or more recognized 

 species, only sixteen have been proved malarial carriers. The more 

 important are Anopheles quadrimaculatus in the United States, 

 Anopheles albimanus in the American tropics, Anopheles maculipennis 

 in Europe, Anopheles senensis in India, and Anopheles costalis in 

 Africa. 



Description of the Mosquito. It is impractical to give more than 

 a hasty description of mosquitoes, and the reader is referred to 

 larger works on the subject (Howard, Dyer and Knab; Theobald 

 or "Medical Entomology," Patton and Oragg, London, Madras and 

 Calcutta, 1913). Malaria at Home and Abroad, S. P. James, 1920. 

 It may be noted, however, that the Culicidw, or mosquitoes, belong 

 to the Dipt era, or two-winged insects. They pass through four distinct, 

 stages in their development, the egg, larval, pupal and adult or imago 

 stage. The eggs are invariably laid in water where, if the temperature 

 is warm, they hatch in one to four days. Anopheles eggs are single 



