koch's control woek 199 



struction of mosquito larvjB (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 

 region. 



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). 



It 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 



