350 



Parasites from 

 person with malaria 



Constant Care Is Needed for Health unit vi 



Sperm cell 



Red corpuscles Parasite 



Spores 

 Sporulation Blood stream 



Fig. 310 A inosqiiho intro- 

 ducing the malarial proto- 

 zoan. What changes take 

 place in the parasite in the 

 hnmaii blood? When you 

 read the second part of the 

 life history of this parasite, 

 study the inosquito. This 

 mosquito had previously 

 sucked up parasites from 

 a malaria patient. What 

 changes do these parasites 

 undergo in the stomach of 

 the 7nosquito? WJ^en these 

 changes have taken place, 

 the mosquito injects the next 

 person it bites. 



Ross, examined great numbers of mos- 

 quitoes in trying to find the parasites. 

 After two years of patient search he dis- 

 covered in the Anopheles mosquito some 

 protozoa which he beheved might be 

 those of human malaria. 



These laboratory demonstrations, how- 

 ever, were still not proof of the con- 

 nection between malaria and mosquitoes. 

 It remained for the London School of 

 Tropical Medicine and for a number of 

 Italian scientists to perform experiments 

 which proved that we get malaria 

 through the bite of a mosquito carrying 

 the particular protozoan and, further- 

 more, that we can get it in no other way 

 but this. See Exercise 5. Could you write 

 out the plans for controlled experiments 

 which would definitely establish the con- 

 nection between mosquitoes and malaria? 

 See Exercise 6. 



The malaria protozoan's life storv — 

 first chapter. The protozoan leads a com- 

 plicated life, half of it in the blood of 

 man and the other half in the stomach of 

 the female mosquito. It is never found in 

 the male mosquito. When an infected 

 female mosquito (an Anopheles in this 

 part of the world) bites and introduces 

 a protozoan, the protozoan soon glides 

 into a red blood corpuscle. Being a para- 

 site, it feeds on the corpuscle and grows 

 rapidly. After a day or two it has grown 

 so much that it may completely fill the 

 corpuscle. It now looks much like a tiny 

 ameba with streaming protoplasm. Then 

 the nucleus divides a number of times, a 

 little cytoplasm surrounds each nucleus, 

 and twelve or more small spores are 

 formed. The membrane of \^hat was 

 once the corpuscle now bursts, releasing 

 the spores and accumulated toxins into 



