MALARIA. 293 



with an organism which can live, and probably also influence of 

 multiply under certain conditions, on the dead nutritive 

 substrata in our ordinary surroundings, and which only 

 at times takes on a temporary parasitic existence. 



As to the substratum which is necessary for the insufficient 

 development of the virus of malaria, we have as yet theh>cai g pre- 

 very few facts which are trustworthy or of use in disposition, 

 connection with artificial cultivation experiments. As 

 a rule in former times it was thought that a warm, very 

 moist, or marshy soil, containing a large amount of 

 organic, and more especially vegetable materials, was a 

 source of permanent danger in any particular region. 

 As the result of the careful investigations of Tommasi- 

 Crudeli, made within the last few years, which have 

 shown that endemics of malaria may occur also in high- 

 lying and by no means marshy districts, and also in 

 regions which have been rendered dryer by planting 

 eucalyptus trees, it is evident that the amount of 

 moisture of the soil which is necessary for the deve- 

 lopment of malaria is very much less than was 

 formerly supposed ; the other factors of importance have 

 been so difficult to define more precisely that we evi- 

 dently require further elaborate investigations in this 

 direction. 



On the other hand, attempts at isolating and cultivating inocuiabiiity 

 the virus of malaria are the more encouraging because, of malari 

 as the result of recent experiments, the possibility of 

 the existence of a true miasmatic virus has been dis- 

 tinctly disproved ; because, therefore, we do not have to 

 do with an unorganised something not capable of multi- 

 plication but produced by a particular soil. Cuboni, 

 Marchiafava, Dochmann, and quite recently Gerhardt ; 

 have demonstrated that malaria is inoculable from man 

 to man. Gerhardt was able to set up a distinct quotidian 

 ague with temperatures up to 41 '1 C. in two healthy 

 men who had been under observation for a long time, 

 and in a locality quite free from malaria, by inoculating 

 them with blood taken during the attack from patients 

 suffering from malaria. 



As the result of the assumption, justified by these 



