MALARIAL FEVEE 159 



ing water; but following the work of Leveran and 

 Golgi a great amount of research was directed to find- 

 ing the mode of infection. 



It was at first thought that the parasite existed in 

 the soil and water; but all attempts to reproduce 

 the disease through the ahmentary tract or through 

 wounds of the skin by means of soil and water were 

 unsuccessful. 



This investigation continued for several years until 

 1897, when Ronald Ross, an Enghsh army surgeon in 

 India, found that malarial infection can occur only 

 through the bite of a certain mosquito (Anopheles), 

 and that the parasite of malaria passes through an 

 extraordinary life cycle in which the mosquito is the 

 definitive host and man the intermediate host. The 

 manner in which the mosquito acquires the parasite 

 and conveys it to man is briefly as follows: On 

 sucking the blood of a malarial subject the parasite 

 is taken into the stomach and intestines of the insect. 

 It passes thence to the salivary glands, where it 

 remains until the mosquito bites again, when through 

 the muscular effort of sucking blood the parasite is 

 readily injected into the tissues of the person on 

 whom the insect is feeding. (Abbott.) 



From these discoveries the former reasons assigned 

 as causes of the disease were easily explained, viz. 



