380 



THE ETIOLOGY OF TROPICAL DISEASES 



P. Manson, the practical investigation and final elucidation of it 

 were in great measure due to the patient observance and skill of 

 Eonald Eoss, at that time a Surgeon-Major in the Indian Medical 



Fig. 34. — Scheme showing Human and Mosquito Cycles of the Malaria 

 Parasite (Manson). 



1-8, the human or endogenous or asexual cycle ; 9-24, the mosquito or exogenous or sexual cycle. 1, 

 Normal red blood corpuscle ; 2-5, blood corpuscles containing an amcebula ; 6-8, sporocytes ; 

 9, young gametocyte ; 11, 13, 15, 17, microgametocytes or male gametes ; 10, 12, 14, 16, macro- 

 gametocytes or female gametes ; 18, female gametocyte being impregnated by microgametes ; 

 19, travelling vermicule ; 20, young zygote ; 21, 22, zygotomeres ; 23, blastophore ; 24, mature 

 zygote. 



Service. His chief contribution to the solution of the problem was 

 the discovery of the malarial parasite in the tissues of the mosquito. 

 He found that in the body of mosquitoes fed upon malarial human 

 blood 70 per cent, of the crescent forms of the parasite, as we have 

 seen one of the latent forms of the flagellated body, were transformed 



