MALARIA AND MOSQUITOES 49 



mon crow, contributed greatly to the elucidation of a 

 knotty point in the life history of the parasite ; the stud- 

 ies of Itoss upon the malarial disease of sparrows in India 

 jn'oved effectively the transmission of this disease by 

 mosquitoes ; Avhile the experimental demonstration of 

 the transfer of the parasite of human malaria by mosqui- 

 toes was first performed by Italian investigators, al- 

 thoiigh it has since been done many times in many parts 

 of the world by workers of many different nationalities. 



The life history of the malarial parasite of human kind 

 maybe briefiy summarized as follows: All of the mala- 

 rial parasites are protozoans, that is to say animals — and 

 not bacteria, that is to say plants. In the human blood 

 these protozoa inhabit the red blood corpuscles and in 

 the blood they go through a sporulating existence, which 

 may continue indefinitely unless checked by quinine or 

 in some other way. In the red corpuscle the parasite 

 appears as an amoebula which gradually grows until it 

 nearly fills the interior of the corpuscle, digesting appar- 

 ently the red coloring matter of the blood and forming, as 

 the result of this digestion, pigment spots in its interior. 

 On reaching full growth the nucleus of the amoebula 

 subdivides, each division gathering about itself a certain 

 amount of protoplasm, until instead of the single amoe- 

 bula the cor[)uscle contains a large number of spores. 

 The walls of the corpuscle then break, and the spores are 

 liberated into the blood serum. From a single infection 

 this sporulation or liberation of the spores takes place 

 practically sinniltaneously and marks the beginning of 

 the malarial spasm. 



