b TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



indeed, is surprised that it is so rare, for there are still in England 

 abundance of Anophelines, e.g., in some of the ditches and 

 marl pits in Wirral larvae abound, and it is the same elsewhere, 

 and the return from the tropics to this country of cases of 

 malaria is by no means rare. How the malaria parasite arose, 

 whether from some form already existent in the gut of the 

 mosquito, is a very interesting problem of which at present 

 we know almost nothing. 



In connection with the disappearance of malaria from 

 England, I might note the peculiar fact that Christophers and 

 myself found in India, in the midst of intensely malarial 

 districts, villages which were completely free from malaria 

 although Anophelines abounded. We could find no explanation 

 of this very peculiar condition, but the same set of conditions 

 is also reported in Italy, and the term Paludismus sine malaria 

 is used to designate them. 



Though this, baldly stated, is the malaria-mosquito 

 cycle, yet we must consider another side to the question in 

 order to fully understand how and why it is that Europeans 

 contract malaria in the tropics. On examining a number 

 of native children who appear to be in the best of health, 

 one is surprised to find that a certain percentage, sometimes 

 80-90 per cent., contain parasites in their blood. These children 

 abound in native villages, and the huts which they inhabit 

 are infested with Anophelines, and a certain percentage of 

 these latter are infected and infective — i.e., contain sporozoites 

 in their salivary glands. If now Europeans live in the vicinity 

 of native huts, as is only too commonly the case in Africa, 

 they soon get malaria. It is the native children that constitute, 

 so to speak, the reservoir of the disease in the tropics. They 

 are the great danger. Prophylaxis is simple: remove the 

 European quarter to a safe distance beyond the usual range 

 of a mosquito's flight — quarter to half a nnTe. This method 

 has been carried out in many colonies with very good results. 



