TRANSMISSION OF TROPICAL DISEASES. 5 



Christophers and myself made many attempts to see the 

 sporozoites penetrating the red cells by mixing the two together 

 in a wet film, but always unsuccessfully. Schaudinn stated 

 that he had seen it, using sporozoites from an oocyst in the 

 stomach (but I would remind you that many of Schaudinn's 

 observations have not been confirmed). 



This development in the mosquito takes about ten to 

 fourteen days, so that it is only after this lapse of time that a 

 mosquito that has bitten a malaria patient is capable of 

 transmitting the infection. This cycle in the mosquito is 

 known as the cycle of new infection. It is again only some 

 ten days after being bitten that the attack of malaria 

 develops. In this way the malaria parasite, when it has 

 got into a mosquito develops and gets out again. 



Malaria or ague has in the past existed in many parts 

 of England, and it is still a memory in the minds of some 

 of that somewhat rare species " the oldest inhabitant." 

 Why malaria died out in England is not, I think, perfectly 

 clear. The factors that are generally invoked to explain 

 its disappearance are the use of quinine, drainage — which 

 decreased the breeding areas of anophelines, the abolition 

 of the window tax, etc. But there is a factor which though 

 general in its action, is probably as great if not greater than 

 any of these — viz., the social and hygienic improvements 

 in the condition of the people. For it has been pointed out by 

 Christophers in India that, caeteris paribus, the ravages of 

 malaria are greatest where the social standard is lowest. 

 Poverty, for instance, is an important determining factor. 

 I have spoken as if malaria had disappeared from this country, 

 but a case has recently been reported from Romney Marsh, 

 an old haunt of the disease, in which the source of infection 

 could not be traced, and one if not two other cases have 

 occurred. The occurrence of malaria at the present time 

 in this country, then, is an extremely rare phenomenon. One, 



