122 MALARIA [CH. 



transmission of malaria had been put forward already by 

 King (1883). That mosquitoes might convey malaria was also 

 definitely suggested by Laveran on the analogy of the develop- 

 ment of filarial embryos in the mosquito (1884). But it was 

 Manson (1894) who more especially elaborated and emphasized 

 the probability of mosquito transmission, and who by his 

 remarkable deductions, based on the behaviour of the flagellate 

 bodies, led directly to Ross's efforts to demonstrate this rela- 

 tion experimentally. 



But none of these hypotheses, not even Hanson's carefully 

 thought out deductions, anticipated the mosquito cycle as we 

 now know it, as a result of Ross's brilliant research, in all its 

 beautiful simplicity. According to Manson it was the fiagella 

 breaking away from the parasite that underwent development 

 in the mosquito, and it was by the medium of water in which 

 the mosquito eventually died that it was supposed re-infection 

 of man took place. Ross's discovery of the cycle of develop- 

 ment of Proteosoma shewed that it was the whole parasite 

 which underwent development, and that re-infection did not 

 take place through water, but that the parasites underwent 

 growth and multiplication in the body of the mosquito, eventu- 

 ally finding their way to the salivary glands, to be injected 

 with the salivary secretion when the mosquito next fed. The 

 significance of flagellation was almost coincidently shewn by 

 MacCallum, who observed in Hcsmoproteus {— Halteridium), 

 another parasite of birds, the fertilization of the female form, 

 or macrogamete, by the fiagella, or microgametes, liberated 

 from the microgametocyte, or male form, of the parasite. 



The discovery of the life-cycle of Proteosoma, and the fact 

 that the protozoa, hke the parasitic worms, might exhibit 

 melaxeny, or the utilization of two or more hosts in their 

 development, gave the clue to the method of transmission of 

 human malaria, and the mosquito cycle of the malarial para- 

 site, as worked out by Grassi and others, was found to 

 follow almost exactly the development previously noted by 

 Ross in the case of Proteosoma. But whereas the parasite of 

 birds underwent development only in mosquitoes of the genus 

 Culex (C fatigans), that of man. required those of the genus 



