312 Major Ronald Boss [March 2, 



ing the matter from every point of view, I must confess to being 

 ignorant of any well-established fact about malarial fever which is 

 not explained by the mosquito-theory. 



This brings me to the subject of objections to the mosquito-theory. 

 In view of the exact and copious microscopical and experimental 

 evidence which has now been collected in proof of the theory, it is no 

 longer permissible to doubt the main facts ; and the objections which 

 one still finds, both in the lay and the medical press, are generally 

 based on a complete ignorance of these facts, and need not be dis- 

 cussed here. But there is one objection — frequently made, in spite 

 of corrections as frequent, by persons who reside in malarious places 

 — which deserves comment. This is, that malaria exists where there 

 are no mosquitoes, and that so-and-so has had fever without being 

 bitten by gnats at all. Generally speaking, we must always remember 

 that malarial fever is a disease in which relapses occur perhaps for 

 years after the first infection, and that it is this first infection and 

 not the relapses which are due to the bite of Anopheles. It is thus 

 possible to suffer from any number of attacks of fever without being 

 bitten by Anopheles (except on one occasion), and without invali- 

 dating the theory — a fact of which those who argue in this manner 

 are generally ignorant. Again, it is well known that one may be 

 bitten without perceiving it ; that some persons are singularly callous 

 to the punctures of these insects ; and, lastly, that many others have 

 very limited powers of observation. I may say at once that, person- 

 ally, I cannot accept any statement to the effect that gnats are absent 

 in any locality in the tropics, until such a statement is made by a 

 competent observer after direct search ; because I have never been in 

 any place in the tropics — and I have been in a large number — where 

 there were no gnats. On the other hand, I have often found numer- 

 ous gnats in localities where I was previously told there were none. 

 I was once actually informed that there are no mosquitoes in Sierra 

 Leone ! The fact is that those who will trust the statements of the 

 general public on such matters must be very credulous. 



I turn lastly to the all-important subject of prevention, but can do 

 no more than touch upon it here. Two methods suggested themselves 

 at once. I need not refer to that of guarding against the bites of 

 these insects by the use of mosquito-nets and so on — an obvious and, 

 I believe, an exceedingly useful measure, which may reduce the 

 chances of infection to a small fraction. Unfortunately such methods 

 will never be employed on a large scale in the majority of malarious 

 localities ; and we must resort to the destruction of malaria-bearing 

 species of gnats. Early in 1892 I reported to the Government of 

 India that it may be possible to exterminate Anopheles in some locali- 

 ties — especially some towns, cantonments and plantations — owing to 

 the habit the insects have (in some places) of breeding only in 

 selected pools. Since then, a considerable literature has already 

 grown up round the subject. Reviewing this literature, it seems 

 probable that we may be able to exterminate Anopheles or at least 



