KOCH’S CONTROL WORK 199 
struction of mosquito larve (petrolizing pools and emptying tanks and tubs 
completely twice a month) ; (2) destruction of adult mosquitoes in the convict 
dormitories with pyrethrum powder, ‘zanzolina,’ chlorine gas, etc.; (3) pro- 
tection of habitations against mosquitoes by screening doors and windows. The 
results in one season were: Anopheles almost never found (and other mosquitoes 
much more rarely than formerly) in dormitories. Not a single primary case 
of malaria developed, the new cases, nine in number, were all importations or 
relapses. The previous year there had been ninety-nine cases, of which about 
forty-four originated on the island. 
Since that time the relation of the mosquito to malaria has become the 
common knowledge of the civilized world, and many regions have been freed 
from the disease by anti-mosquito work. Some of these have been mentioned in 
other sections of this work. 
Koch, in 1900, at Stephansort, in German New Guinea, conducted a vigorous 
anti-malaria campaign to determine if malaria could be eradicated from a given 
locality. His work was based on the idea of destroying the parasites in the blood 
of man by means of quinine and thus depriving the mosquitoes of the source of 
infection. In the first place, by the microscopic examination of the blood, all the 
persons of the community in whom malaria was latent were discovered. These 
potential transmitters of the disease were treated with quinine, administered 
methodically at regular intervals until the parasites had disappeared from the 
blood. Every one of these, at intervals of ten or eleven days, was given one gram 
of quinine on two successive mornings. When necessary the intervals were 
shortened and the doses of quinine increased. In this manner Koch succeeded, 
in the space of a few months, in almost wholly eradicating malaria from 
Stephansort. The results of Koch’s experiments indicated that this method of 
destroying malaria, so that there is no disease for the Anopheles to transmit, 
may be most useful under certain conditions. Koch protests that his method 
differs radically from the so-called quinine prophylaxis with which it has been 
frequently confused. This latter method aims to prevent the infection of man 
and, to be effective, would have to be applied to all the inhabitants of a malarial 
Tegion. 
Dempwolff later continued the work of Koch in German New Guinea. He 
found, when he tried to apply the Koch method on a large scale, that the method 
has its limitations. He found much difficulty in making the necessary blood 
and spleen diagnoses, not only in the prejudice and superstition of the natives, 
the shifting character of the population, but often in the indifference of the 
European settlers as well. Dempwolff points out that the prospects are much 
more hopeful when the Anopheles appear only at a certain season and one can 
hope to break the chain of the malarial organisms from one season to another. 
He points to the results, under such conditions, of Vagedes in Franzfontein 
(German South-west Africa), Frosch in Brioni (Istria) and Ollwig in Dar- 
es-Salaam (East Africa). 
Tt should be here stated that cinchonization was tried in 1903 by Edmond 
and Etienne Sergent in France at Saint-Philbert de Grand-Lieu, but their 
