918 QUEENSLAND AGRICULTURAL JOURNAL. {1 Mar., 1898. 
directly inoculated into man by the mosquito, an idea in support of which he 
adduces the analogous case of Texas fever in cattle being directly inoculated 
by ticks. Bignami’s remarks are so extremely apropos of the subject we are 
now considering, that it will be well to quote his own words. He says :— 
_ “As regards malarious infection the idea that insects, and especially 
mosquitoes, have an intimate relation with the mechanism through which man 
takes the fever has been started by many observers, particularly by some of the 
Americans. Laveran, who, as is well known, is the principal supporter of the 
water-conduction theory; notes the abundance of mosquitoes in marshy places, 
calling attention to the fact that the drainage of the soil, whilst it suppresses 
the fever, also suppresses the mosquitoes. He also calls attention to the 
possibility (without excluding it) that mosquitoes have a part in the patho- 
_ genesis of malaria as they have in that of filariasis, and, as believed by I’:ndlay 
and others, also in the dissemination of yellow fever. Grassi and I’eletti exclude 
this possibility without even considering it, because places exist infested with 
mosquitoes where one doesnot take the fever. The fact is known to all, but it is 
not sufficient,to exclude the hypothesis that mosquitoes are the carriers of the 
infection. It would further be necessary to demonstrate that in the soil or in 
the-waters of those places there exist malarial germs, of which these insects 
are only the vehicles and inoculators into man.* Besides this they recall a fact 
asserted by Calandruccio, that in the intestine of mosquitoes malarial parasites 
die without developing further. (A similar fact has. also been observed in 
leeches.) But the observation of Calandruccio can be fairly opposed to those 
of Ross and the hypothesis of Manson, whilst, if I am not mistaken, it has no 
yalue against the hypothesis that man is inoculated with malaria by the 
mosquito. On the other hand, the knowledge, if it could be well authenticated, 
that there exist places in which malaria can be contracted notwithstanding the 
absolute absence of mosquitoes and of insects which could inoculate it, would 
suffice to exclude the hypothesis. But one has no authenticated information 
of such an occurrence. On the contrary, all authors speak of the abundance 
of these diptera in the malarial districts. Kelsch and Kiener, in their well- 
known treatise, do not even allude to the possibility of inoculation. They also 
éxclude the water-conduction hypothesis. ‘hat the infection comes by inhala- 
tion through the lungs they have no doubt. ‘ 
“ Notwithstanding the authority of the observers cited, it has for a long 
time appeared, and still appears, to me that an attentive examination of the 
question which I have mooted above will not be wholly useless. If one admits 
the inoculation hypothesis, many facts which are difficult to explain by the 
theory of air conduction would find a simple and satisfactory explanation, and 
itis easy to demonstrate this. J irst of all, the fact, which we have already 
discussed at length, that malaria is not carried by the winds would be easily 
understood, knowing as we do how closely these diptera are bound to the soil 
on which they are hatched, and how averse they are to allow themselves to be 
carried away, hiding when the wind blows, in the ground, amongst the grass, 
or under the. trees; also, when a sea breeze blows in the afternoon the 
mosquitoes of the Roman Campagna do not show themselves, and only when 
the wind has gone down at the setting of the sun do they rise in clouds 
everywhere and attack animals and men. ‘That the evening and night hours 
are the most dangerous, on account of the facility with which fever is then 
taken, would be easily understood by anyone who knows the habits of this 
nocturnal dipter. That malaria only rises to a moderate height would also be 
equally intelligible, because the inoculating insect always flies near the ground. 
A: satisfactory explanation would also be furnished of the great danger of 
sleéping in malarial districts, a fact of which the supporters of the air-con- 
duction theory have never been able to give more than an artificial explanation. 
.'*The same facts, mutatis mutandis, and the same reasoning apply to the well-known 
eee that ticks may-ba present in a locality without producing—at any rate, obvious— 
isease; i Re ie Seda i 
