434. MOSQUITOES OF NORTH AMERICA 
of such a system was to destroy all mosquitoes which might have carried infec- 
tion within the district. 
“While the disinfecting force is thus at work the police division, under the 
direction of a physician and of students who direct the different sections, operates 
throughout the infected district, making every effort to destroy all mosquito 
larvee and to prevent the possible breeding of mosquitoes outside as well as inside 
the houses. Where larve are likely to exist in stagnant water or refuse of any 
sort, petroleum mixed with creoline, lysol, or similar products is thrown over the 
water or refuse in sufficient quantity to kill the larve instantly. Where it is im- 
possible to use petroleum, as in the case of tanks and boxes for household use, a 
small fish, the ‘ barrigudo’ or ‘ Girardinus caudimaculatus’ is placed in large 
numbers in the water. This fish destroys the larvae of mosquitoes most vora- 
ciously. Larve in the drains are destroyed by the use of Clayton gas, which is 
pumped into the sewer, which has been previously divided into compartments. 
Simultaneously with the disinfection the sanitary inspectors make daily in- 
spection of the suspected district, examining every inhabitant supposed not to 
be immune, that is, children under 5 and all foreigners of less than 5 years’ resi- 
dence in Rio. These are subjected to the closest vigilance, being placed in 
isolation at the least tendency to rising temperature. Reports are made in 
writing, those to whom this duty falls being required to fill out daily a bulletin 
sent out by the medical inspector to the chief of each district. In this report 
must be given the record of any who work outside the district or who for any 
reason absent themselves therefrom, a record of their condition being also kept 
by the physician in the district in which they work or are temporarily resident. 
When any inhabitant absents himself from the district the record must show his 
address, where he will be subjected to vigilance on the part of the authorities 
there, If the person under vigilance evades the attention of the physician and 
withdraws without giving notice, the owner of the house in which he lived is 
fined, he himself is apprehended by the sanitary police, fined, and subjected to 
renewed vigilance. 
“ The vigilance in each district extends over a period of one month after the 
appearance of the last case. To give an idea of this service we will note the 
figures covering the prophylactic campaign in the infected district about the 
cotton factory, ‘ Fabrica das Chitas,’ in 1906. The inspection was carried out 
by 18 doctors, who examined daily all suspected persons, in all, 7966 persons, of 
whom 2989 were not immune. Sixty cases were reported, of which only 19 
proved to be yellow fever, and the district was declared entirely freed of infection 
after six months. With the combination of the three systems there is no doubt 
about cleaning up effectively any district in which yellow fever may appear. 
In normal conditions the police service is carried out with equal painstaking, 
especially in the districts where infection last appeared. When, after some time, 
there seems no longer to be danger of new infection, the inspectors allow water 
to stand in several marked spots most favorable to mosquito breeding. These 
pools are then carefully watched, and examined at frequent intervals. This is a 
sure way to indicate the presence of the mosquito and is a trap for those about to 
spawn. They are thus most easily destroyed. In many zones of the city these 
traps revealed the presence of no mosquitoes whatever.” 
The actual results which followed this admirable work are shown by a table 
indicating the death rate from yellow fever in Rio from 1872 to date, and which 
indicates that perfect success has been reached. 
