162 



cobwebs in the dark, windsheltered corners of the stable. A closer examination 

 showed that of Culicidce the stable only contained A. maculipennis; that almost all 

 were females and only a very few males; further that almost all females were 

 blood-filled. 



In the following weeks I then explored about twenty farms lying in the middle 

 of Seeland; later on ten in the north of Seeland. In every stable I found the mos- 

 quitoes; the number varied, but was very often about 100 specimens upon one 

 square yard; very often I saw stables in which the number must be estimated to 

 be many thousands in all. 



The fact interested me very much, never having thought that my limnologi- 

 cal studies would carry me away from the moors and lakes into the stables; that 

 however was the case for more than two years. I immediately saw that here prob- 

 ably was the clue to the enigma why one of the most terrible epidemics, from which 

 our country had suffered, had totally disappeared from the country in such a 

 relatively incredibly short space of time. 



On two journeys to Lolland-Falster, formerly the real home of the malaria, 

 I studied the behaviour of Anophelines there; in 19191 explored another old malaria 

 centre, the marshes in the western part of Jutland. In 1920 I further requested Mr. 

 KRYGER, on a journey which lasted about a month, to explore the life modus of 

 Anopheles maculipennis in the southern part of Jutland, from Kolding along the east 

 coast to Skanderborg; further an area round the large lakes near Silkeborg, then 

 westward over the heath and finally near the large downs along the west coast 

 of Jutland. 



For my own part I chose a single farmyard lying near my laboratory at 

 Tjustrup, used the stables as a laboratory and visited the stable in the time from 

 June to September, often almost every day and at all events every seventh day; 

 further I visited it now and then also at other times of the year, and moreover 

 at all hours of the day and night. I wish to give my heartiest thanks to the owner 

 of the farm, the chairman of the parish council Mr. JORGENSEN. Of course without 

 any scientific education, yet he was soon interested in the exploration, often looked 

 for the mosquitoes himself, and allowed me to begin, carry on, and complete my 

 investigations at every time of the year and the day. In this connection I also wish 

 to bring my best thanks to Mr. PETERSEN, veterinary surgeon at Ringsted, Mr. J0R- 

 GENSEN, Nysted, Mr. E. PETERSEN, Silkeborg, and Dr. HELMS at Nakkeb011e Fjord; 

 Prof. C. O. JENSEN, Copenhagen; they have all given me information of different 

 kinds. In April 1920 I delivered a discourse in the Royal Society at Copenhagen 

 on the malaria mosquitoes and their relation to the Danish malaria. Some weeks 

 later, Prof. C. J. SALOMONSEN called my attention to a paper by E. ROUBAUD published 

 in April 1920, the very same month in which I delivered my discourse. I immedia- 

 tely saw that it had happened that two scientists in two countries, without having 

 the slightest suspicion thereof, had studied quite the same phenomenon simultane- 

 ously and on quite the same principles. It was with the greatest satisfaction that 



