2 Major Ronald Ross [March 2, 



These observations were confirmed and extended by a large number 

 of persons working in various parts of the world most prominent 

 among whom are Marchiafava, Celli, Vandyke Carter, Grassi, Osier, 

 Bignami, Antolisei, Councilman, Mannaberg, Rcmanowsky, Labbe, 

 Koch, Manson, Thayer and MacCallum. In short, the work of all 

 these observers, and of many others scarcely less meritorious, has not 

 only absolutely established the fact that the parasites are the cause 

 of malarial fever, but has given us a very thorough knowledge both 

 of the parasites themselves and of their pathological effects, direct and 

 indirect ; until the science of malaria for it may almost be de- 

 scribed as a science in itself has become a brilliant exemplar of the 

 modern methods of research as regards the science of .disease in 

 general. 



But I am not here concerned with questions of pathology in 

 malarial fever. At tho conclusion of the labours to which I have 

 just referred, we had, it is true, grasped the nature of the disease 

 itself; but a question of the greatest moment still required an 

 answer. We had studied side by side the morbid process and the 

 parasites which cause it ; but we had still to find out how infection 

 is caused, how these parasites effect an entry. We had ascertained the 

 life-history of the parasites within man, and of the kindred parasites 

 within other animals ; but, even after all these investigations, the 

 life-history of the parasites outside man and outside other vertebrate 

 hosts remained to be discovered. Until this was done our knowledge 

 was not complete. It is now my privilege to describe the interesting 

 theories and investigations which led to the solution of this great and 

 difficult problem. 



The importance of the problem need not be enlarged upon. In 

 the British army in India during the year 1897, out of a total strength 

 of 178,197 men, no less than 75,821 were admitted into hospital for 

 malarial fever ! Fortunately the death-rate of the disease is low in 

 most places ; but on the other hand the cases are so numerous that 

 in the aggregate the mortality from malarial fever is very large 

 indeed. For instance, in India alone, among the civil population 

 (who do not take adequate treatment), the mortality from " fevers " 

 during the single year 1897 amounted to the enormous total of 

 5,026,725 over five million deaths being nearly ten times that due 

 to any other disease. Although undoubtedly thousands of deaths are 

 wrongly attributed to fever in these statistics, such figures can point 

 only to a very great mortality due to malaria. Yet India on the 

 whole is not nearly so malarious as many localities such, for in- 

 stance, as places on the coasts of Africa. In short, next perhaps to 

 tuberculosis, malarial fever is admittedly the most important of 

 human diseases. 



But if the problem to which I refer was an important one, its 

 solution presented difficulties which I, for one, formerly thought to 

 be insuperable. It has been mentioned that Lancisi and Pringle 

 connected tho disease with stagnant water; and their views have 



