MOSQUITOES 79 



It has been found that the parasite goes through certain 

 stages in the blood of man, but that finally it is taken up 

 by mosquitoes and in the bodies of these insects it goes 

 through certain stages quite different from those gone 

 through in man. 



Finally, we know that the parasite is injected into the 

 blood of a person by a certain kind of mosquito. 



Since this parasite lives only in man and the mosquito, 

 it can get from one person to another only through the 

 agency of these insects. In other words, a person once 

 free from the malarial parasite will remain free just so 

 long as the bites of certain species of mosquitoes can be 

 avoided. 



Number of germs in the blood. — The number of 

 malarial germs in the blood may vary at different times. 

 The more germs there are, the harder will be the chills 

 and fever as a rule. It is easy to see that the more in- 

 fected mosquitoes there are to bite a person, the more 

 germs there will be in the blood and the more severe will 

 be the case of malaria. This is important to bear in 

 mind because it is closely connected with what we shall 

 have to say in regard to methods of prevention. Ross 

 says he "computes that something like a quarter of a 

 billion of them must be present to produce fever." 



There is another fact that we should also bear in mind, 

 namely, that the germs may actually be present in the 

 body and yet not produce chills and fevers. They may 

 lie dormant in the body, as it were, for a long time and 

 then suddenly become active, increase and produce fever. 

 Under such a condition of affairs circumstances might 

 seem to prove that a person could have malaria without 

 being bitten by mosquitoes. It must be remembered, 



