187 



and Central-European malaria. As mentioned above, even nowadays small epidemics 

 of malaria now and then break out in the regions round the Baltic or North Sea. 

 (Holland, Ditmarshen, Wilhelmshafen, Finland); only Sweden and Denmark have 

 been spared. The curves of these epidemics are very peculiar. Already C. A. Han- 

 skn showed that the climax of the malaria curves with regard to the old Danish 

 epidemics was in May, and Flensburg has shown the same with regard to Swe- 

 den; it was and is even nowadays the same with the greater part of Germany. 

 (See especially Martini 1902 p. 147). On the other hand in Italy the climax lies 

 in Aug. — September. In all cases we have to do with the curve of fresh cases (not 

 relapses) and with tertian malaria. Ziemann (1918 p. 123) points out that it seems 

 as if the climax of the curve the nearer we get towards the north, has a greater 

 and greater tendency to be displaced towards the left side. Koch (1899), who 

 is well aware of the phenomenon, supposes that it must be understood as follows: 

 The inhabitants north of the Alps, by heating their houses, create in them tempera- 

 tures for the mosquitoes lying above the temperatures to which the, mosquitoes in 

 more southern countries are exposed at the same time of the year, and tempera- 

 tures by which it is possible for the parasites in the mosquitoes to develop. 



Schoo (1902 p. 1343) has arrived at quite the same result: He shows that 

 Anophelines caught indoors in Holland, and which were freshly infected, got "Sichel- 

 keime" in the course of twelve days. It was only necessary that the mosquitoes, 

 immediately after the infection, only for two days should be exposed to a tp. of 

 25° C. If this was the case the tp. might sink from 22 to 10° C. without damage 

 to the parasites. At a constant tp. of 18° C. the parasites in Anopheles used 18 days 

 for development and at 30° C. only ten. 



The suppositions may have been correct for the old malaria epidemics north 

 of the Alps; it is also possible that they hold good for the smaller epidemics in 

 Holland and Germany at the beginning of the last century. But I venture to remark 

 that if we in our country should get another malaria epidemic and the curve should 

 show the vertex in the same place (in May) as in the curve for the old epidemic in 

 the middle of the ninteenth century, this explanation could not be used. - - Our Ano- 

 phelines do not hibernate either in dwelling rooms or in stables, they hibernate in 

 outhouses and similar localities; here they hang till the latter part of April, not 

 leaving the hibernating places to enter our stables before then. They do not begin 

 to sting before the middle of May. For Finland Levander states that the Anophelines 

 do not arrive in the rooms before the first days of July. It must be taken for 

 granted that they all are free from plasmodia and first must infect themselves. That 

 an Anophelin material of this kind should be able to cause a climax of the curve 

 already in May is highly improbable. On the whole I am not quite sure that the 

 explanation of Koch and Schoo of the malaria curve for North Germany and Holland 

 really holds good. Further explorations are desirable. — It must be remembered that 

 we have not the slightest understanding of the fact that the enormous amount of 

 Anophelines which are hatched during summer, and in comparison with 



