78 
PROPHYLAXIS OF MALARIA. 
protected there developed 319 cases of malaria. The men were con¬ 
fined in the screened barrack from half an hour before sunset to 
half an hour after sunrise during this time, and wore head-nets 
and gloves when on service at night. 
Orenstein 39 gives a most interesting account of the value of screen¬ 
ing as illustrated in the settlements of Gatun and New Gatun, in 
the Canal Zone. Gatun had a population of approximately 4,500, 
residing in screened quarters, while New Gatun, having a popula¬ 
tion of about 5,000, had no screened quarters. With this exception 
the surroundings were identical so far as chances for malarial infec¬ 
tion were concerned. Observation extending over three years showed 
that the malarial incidence for Gatun and New Gatun was as 2 is 
to 3, the following being the yearly incidence in each settlement: 
Year. 
Gatun. 
New 
Gatun. 
1909. 
Per cent. 
5.35 
5.37 
8.75 
Per cent. 
10.04 
9.21 
12.59 
1910. 
1911. 
In his conclusions Orenstein says: 
A properly screened dwelling can be depended upon to reduce by at least one- 
third the malaria incidence in a locality where malaria is endemic. 
These instances illustrate how valuable a prophylactic method we 
possess in screening when it is efficiently applied, but it should be 
remembered that it is far less valuable than is the abolition of the 
breeding places of mosquitoes when this can be accomplished. How¬ 
ever, as has been repeatedly stated, it is only under exceptional con¬ 
ditions that one is able to entirely rid a locality of mosquitoes, and 
it therefore follows that screening must always remain one of our 
most valuable accessory methods in the prophylaxis of these infec¬ 
tions. In the field, of course, we must depend entirely upon the 
use of the mosquito net and quinine in the prophylaxis of malaria 
among troops, but in permanent posts screening should not be de¬ 
pended upon to the exclusion of other prophylactic measures, but 
should be used along with them. 
Screening of malarial patients .—In concluding this chapter I de¬ 
sire to call attention to the very great importance of screening all 
malarial patients as long as the plasmodia can be demonstrated in 
any number in the peripheral blood. It is obvious that if we place 
the infected individual in a position where mosquitoes can bite him 
the mosquitoes will become infected, provided gametes are present, 
or the patient may become reinfected by the bite of an infected mos¬ 
quito. Despite these facts I have several times observed malarial 
patients in a common ward lying unprotected by a mosquito net, 
