February, 1912.] Annual Address. xlix 
I pass on to the subject of fevers, malarial and other. 
As you probably know it was Laveran who first discovered the 
amplified as they were, especially in Italy, by observers like 
Marchiafara, Celli, Golgi, an ignami, etc., and which were 
followed up by the painstaking work of Sir P. Manson and 
others, and all of which paved the way for the epoch-making 
discovery some years later by Sir Ronald Ross of the I.M.S.) 
have revolutionized our ideas about malarial infection. Pre- 
whence do they originate ? and how do they invade the human 
2 
y? 
The three hypotheses were— 
1. Aerial infection. 2. Drinking water infection. 
3. The mosquito theory. 
It is unnecessary for me to discuss the first two of these 
theories, as the evidence in their favour is quite inconclusive, 
and the theory which holds the field is the last. It is said by 
some that this is by no means a new theory and that it is men- 
tioned by some of the older writers (such as even Susruta, Colu- 
mella and Viturins, and in later times by Lancisi) who all believed 
that malaria was transmitted by the stings of insects. Whatever 
credence we may place on these assertions, there is no doubt 
that it was Ross’ daring leap which established at a bound the 
inoculation into the human subject of the phase of the malarial 
malaria from infected places such as Ismailia and elsewhere. 
Unfortunately these measures are not so easy to carry out on 
a large scale in the enormous swampy areas of lower Bengal. 
In fact are impracticable. The malaria parasite is transmitted 
by a special kind of mosquito—not every mosquito. There 
are some three or four hundred different species of mosquito, of 
which the females are mostly known, and probably half as 
many undescribed species. Luckily only a small portion of 
