706 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
by the breaking open of the cyst,are carried by the blood toward the 
head, then into the proboscis of the insect, which inoculates them with 
every bite. The second proof is this: One can voluntarily produce 
malaria by causing healthy mdividuals to be bitten by Anopheles 
intentionally infected. This experiment was carried out by Patrick 
Manson on his own son. The third proof is as follows: Malaria can 
be avoided by taking the single precaution of protecting one’s self 
from the bites of mosquitoes. 
This results from the experiments of Sambon and Low, who, with- 
out the least accident, were able to pass an entire summer in one of 
the most insalubrious places of the Roman campagna, by simply cov- 
ering the openings of the house with wire netting of sufficiently fine 
mesh to prevent the access of the Culicide. 
In order to remove all doubts Sambon and Grassi undertook, in 
1900, a series of experiments which showed absolutely -the réle of 
the Anopheles in the propagation of fevers. They were made on the 
disciplined personnel of the railroad companies south of Naples, in a 
region where the disease is so endemic that it is called “piano di 
pesto.” They consisted exclusively in protecting all the inhabitants 
of a given zone from mosquitoes, while those of the neighboring 
localities, who were not protected, served as proofs. The results 
furnished by these experiments were marvelous. In 113 individuals 
of the protected zone not a single case was produced, while the persons 
in the neighboring unprotected zone fell sick in the proportion of 
49 to 50. The proof could not have been more striking. 
As regards the objections which have been made to the mosquito 
theory, the most serious is that in certain marshy lands there is no 
trace of Anopheles. In order to verify the truth of this observation 
Laveran organized, around the entire earth, a vast inquiry for the 
purpose of establishing a list of the mosquitoes peculiar to every 
marshy region. Thus far the inquiry has shown, first, that there are 
Anopheles in all insalubrious countries; second, that nearly always 
abundance is in direct ratio to the frequency of fevers; third, that 
the pretended absence of these dipterous insects was due simply to 
inadequate collecting, often undertaken but once and at a single point 
in the region. 
Another objection is, so to speak, an inversion of the last. In 
certain salubrious localities there are Anopheles in abundance. That 
is readily explained, however, because it is evident that mosquitoes 
can not become dangerous until after they become infected—that is, 
after having sucked the swamp blood. But if there be no malaria 
in the country they can not become contaminated, and hence remain 
inoffensive. 
To summarize, one can affirm to-day, without fear of being mis- 
taken, that the doctrine of anophelism triumphs everywhere, and 
