128 THE MAIN CURRENTS OF ZOOLOGY 



circumstances under which was demonstrated the 

 transmission by insects of Malaria. Malaria is a 

 widely-spread infectious disease. This disease, char- 

 acterized by periodically recurring chills and fever 

 was called Malaria, which means bad air, from the 

 belief that the Malaria was due to miasmatic vapors 

 arising from swamps and marshes. The disease, 

 formerly called fever and ague, was observed to be 

 most prevalent in marshy districts and in places with 

 standing water. It is now known that this is owing to 

 the fact that wet places supply the conditions for the 

 nurture of the mosquitoes that transmit the disease. 



That it is transmitted by a particular kind of 

 mosquito was well established by Ross in 1898. 

 There were several steps leading up to this final 

 demonstration each one of which is an interesting bit 

 of biological advance. 



It was in 1880 that Laveran, a French military 

 surgeon, then serving in Algeria, made known the 

 presence of a micro-organism within the blood of 

 patients suffering from malaria. This so-called 

 plasmodium is a microscopic animal (protozoan) 

 parasite. In the blood of an infected person the 

 minute malarial parasite bores its way into a red 

 blood corpuscle and feeds and grows at the expense 



