34 
REPORT OF THE MALARIA EXPEDITION. 
On the other hand, it is impossible to consider the matter given in paragraph 2i without 
feeh'ng that the gnat-theory suffices to explain almost all the better-established laws regarding 
malaria — its connection with the soil, with stagnant water, with rainfall, with rural areas, and 
so on. In short, there seems to be no longer any necessity for believing that the parasites live 
at all in the air or soil of infected localities. The facts on which we formerly founded our 
belief that they did so are now otherwise explained by the origin of Anopheles from surface- 
puddles. The facts were sound enough ; our interpretation of them was wrong. Malarial 
fever is connected with the soil, with stagnant water, and so on, as we supposed it is ; but 
it is 7ioty ns zue thought^ the germ itself which springs from the soil — but the carrier of the germ. 
It is impossible to avoid seeing how completely this fact in the bionomics of Anopheles 
subverts the argvunents in favour of the view that the pathogenetic organisms themselves have a 
telluric or paludal origin. 
The idea that the parasites can originate in the soil, and thence pass into gnats, and 
from gnats to man, is opposed to all parasitological analogy. On the other hand, that they 
can pass alternately between men and gnats is merely an instance of a very common law 
among parasites. 
The fact that malarial fever is communicable from the sick to the healthy has certainly 
been a surprising one. We thought that it is not communicable because we observed that 
communication does not occur outside endemic areas ; while within endemic areas we attributed 
to an endemic poison infections which were really due to communication from the sick. By 
endemic (malarious) areas, we now understand simply areas which are infected by the com- 
municating agent [Anopheles). 
Of course the parasite itself, as well as both the hosts, must be present in an endemic 
area. Once present, however, there is no reason why it should not remain indefinitely so long 
as botli the hosts remain. 
So far, then, all the known facts about the prevalence of the disease seem to be easily 
explicable b}- the bionomics of the parasites and of Anopheles ; but we now come to the 
consideration of the one popular theory which is not so readily explained — we mean the notion 
that malarial fever may be acquired in uninhabited places. 
As a rule man lives in the society of man. Hence the vast majority of infections must 
take place in inhabited places — in places where previous cases of malarial fever have existed 
perhaps from time immemorial. Even during the most detached moments men are seldom 
quite solitary. Pioneers, explorers, missionaries, travellers, sportsmen, are usually accompanied by 
trains of servants and carriers ; in order to reach uninhabited places they have to pass through 
native towns and villages ; have to live long perhaps Hn native houses, and in settled camps 
surrounded by their followers. Ships on which malarial fever breaks out have not as a rule 
touched at iminhabited spots on the malarious coast, but at towns and ports where trade is carried 
on — and may have been visited by infected coolies, or even by infected gnats, from the shore. 
In all such instances, cases of fresh infection may be simply explained by communication from 
previously infected men — at least the possibility of this can seldom be excluded. Even in the 
