RELATION OF ARTHROPODS TO PATHOLOGY—MAROTEL. 705 
theories of which to-day nothing remains. The first ray of lght 
appeared in 1880, at which date one of our members, Laveran, dis- 
covered at Constantine the hematozoan which to-day bears his name 
(fig. 1). But the veil of obscurity which enveloped this important 
question could not be completely dissipated until 1898. 
It was at this time that a group of students, at the head of whom 
should be placed Grassi and Manson, demonstrated in an irrefutable 
manner that the parasite of malaria was intro- 
duced into man by mosquitoes; that is, passed 
from man to the mosquito and from the mos- 
quito back to man again, and thus on indefi- 
nitely, without being for a single instant, even Pants Re sce 
the thousandth of a second, liberated into the zoan of human ma- 
external environment. Consequently, in spite aie ie a 
of what was thought for centuries, none of these 
mediums, neither the air, the water, nor the soil, can cause ma- 
laria, and these beliefs become henceforth a part of the history of 
medicine. 
There is one extremely important fact: Not all species of mosqui- 
toes can propagate malaria; only those which, in the family Culicide, 
belong to the tribe Anopheline can assume 
this role, and the most dangerous of the 
species from this point of view are first of 
all the Anopheles maculipennis, which is 
by far the most redoubtable; then A. pseud- 
opictus, A. superpictus, A. bifurcatus, A. 
funestus, and finally a last species, Pyreto- 
phorus costalis. 
The proofs which one can give to-day of 
the mosquito theory are three. The first is 
that of Grassi, who, in 1898, in association 
with Bignami and Bastianelli, was able to 
follow the evolution of Plasmodium day by 
day in the bodies of mosquitoes which had 
been made to suck blood affected by ma- 
laria, showing thus that the parasite could 
me al he. eres les! penetrate the insect, remain there a certain 
(After Neveu-Lemaire.) t, time, and then leave to pass immediately to 
etn pa- man. These students have also established 
oa a the fact that while in the Anopheles, the 
hematozoan undergoes profound transformation, constituting a veri- 
table evolution, and that the intimate mechanism of the transmission 
was as follows: The parasites sucked in with the blood lay eggs in the 
stomach, which eggs encyst themselves in the walls of the stomach, and 
produce a multitude of little vermicular spores. These, set at liberty 
