MOSQUITOES AND MALARIA. 



By JOHN SHIRLEY, B.Sc. 



liead before the Roi/al Societi/ of QueensJond, June 17, 1899. 



CAUSE OF FEVER. 



In the blood of malarial fever patients is always found an 

 organism, discovered by Laveran in 1810, and consequently 

 known as the phismodium vudaria'. 



THREE STAGES. 



This organism is found to exhibit three phases, one 

 adapted for life with man as its host, a second adapted for life 

 outside the human body, and probably a third or latent stage. 



HUMAN CYCLE. 



Every variety or species of the plasmodium inhabiting man 

 has its special and more or less definite life span of 24 hours, 

 of 48 hours, or of 72 hours. On examining malarial blood 

 towards the end of one of these cycles, before one of the 

 paroxysms of the characteristic periodic fever is induced, the 

 parasite may be recognised as a pale ill-defined disc of proto- 

 plasm, occupying a larger or a smaller area, within a proportion 

 of the red blood corpuscles. Scattered through this pale body 

 are a number of particles of intensely black, or reddish black 

 pigment — melanin. 



On repeated examination at short serial intervals the 

 observer notes a systematic series of changes in the discs of 

 pigmented protoplasm. 



1, The scattered pigment particles collect into little groups, 

 or into radiating lines ; 



2. The pigment groups concentrate further into one or two 

 larger, more or less, central blocks ; 



8. Around these central masses the protoplasm groups 

 itself as globular masses, i.e. spores ; 



