124 HISTORY OF MALARIA [CH. 



This view, that malaria is a disease transmitted by Anopheles , 

 but essentially of an infectious nature depending on pre-existing 

 human infection for its origin, may be said to be that upon 

 which all present day conceptions regarding the epidemiology 

 and prevention of malaria are based. Such a conception of 

 malaria is of course entirely opposed to the older notions of 

 a " telluric " disease, and as a result the whole method of 

 approaching malaria problems has so changed that writers 

 sometimes refer to researches they may have conducted as 

 being directed from the New Mtiological Standpoint. 



But though all the more modern work upon malaria has 

 been based upon the discovery of the mosquito cycle, yet it 

 would be a mistake to suppose that no considerable advance 

 in the knowledge of malaria has been made since this great 

 discovery. Not only has there been a vast accumulation of 

 knowledge regarding the circumstances connected with malaria 

 in almost all parts of the world, but even in some cases a distinct 

 modification, or rather expansion, of original conceptions of the 

 disease has resulted. Thus the idea of malaria as an infectious 

 disease requiring some previous case of fever from which infec- 

 tion was to be derived, has been modified, at least as far as 

 tropical countries are concerned, and brought more into touch 

 with the old telluric views by the discovery of the almost 

 ubiquitous latent infection of native indigenous races and of 

 the part played by native communities as " reservoirs of 

 infection." Equally important have been the striking advances 

 in the conception of the part played by economic influences in 

 determining the degree of prevalence of malaria, for as stated 

 by Celli it is not merely malaria parasite + Anopheles + man 

 which determines the prevalence of malaria, especially the 

 prevalence of this disease in epidemic form, but the formula 

 malaria parasite + Anopheles 4- man + X. It is in fact the com- 

 plicated factors involved in this unknown X with which the 

 most recent investigations on malaria have been mainly con- 

 cerned, and the complete elucidation of Celli's formula will 

 constitute still another step of no mean importance in the history 

 of malarial research. 



Again, with regard to advances in connection with 



