20 



Anophelines in this province apparently prefer horses to cattle in 

 sheds where both are present. Cowsheds are also less infested because 

 they are less dry ; further, in the area investigated, cows are pastured 

 until late October or mid-November, by which time the Anophelines 

 have already chosen their winter quarters. 



In dwellings Culicines are found in the cellars and Anophelines in 

 the attics, especially in those that are slept in. Anophelines are 

 not usually numerous, but in a garret in a working-class dwelling at 

 Amsterdam 350 were caught in February. 



The disinfestation of stables at Amsterdam was done with a vacuum 

 cleaner or with petroleum. For petroleum a flat tray was used con- 

 taining wadding soaked in the liquid. By holding the tray close to 

 the ceiling for a few seconds the mosquitos were caused to fall into it. 

 Both these methods permitted counts of the numbers present. In 

 one stable the catches ranged in consecutively decreasing numbers 

 from 6,500 on 21st February to 250 on both 23rd and 29th April. 

 As new adults could not appear before May, those captured at the 

 later dates must have escaped the first disinfestations or have come 

 from other places. 



On 30th March the first find was made of larvae, apparently those of 

 A. hifurcatus, which hibernates in the larval stage. It is of little 

 practical importance in Holland, as it is not a domestic species. At 

 the end of June larvae of A. macttUpennis were taken in water among 

 sand dunes from one to two miles from the nearest building, so that this 

 species is not necessarily a domestic one. In and around Amsterdam 

 the first larvae were found on 4th May and the last on 14th October. 

 The first males occurred on 27th May in a stable and on 7th June 

 in a dwelling. Males of Cidex were taken indcors on 12th May. 



As regards the incidence of malaria, it is stated that 2,309 Anopheles 

 were caught in houses where there were cases of this disease. In 

 summer the percentage of infection in such mosquitos was only • 7, 

 but a maximum of 7 was reached in November. 



In the province of Nortli Holland the dykes are cleaned and repaired 

 in September. If the work could be dene a month earlier, when the 

 larvae are most abundant, large numbers would be destroyed. If a 

 second cleaning is possible and could be arranged for the second half 

 of May, a large portion of the first brood would be destroyed. 



KoRTEWEG (P. C.) & SwELLENGKEBEL (N. H.). Wanncei heeit ten 

 onzent de Malariabesmetting plaats ? [At what Period does 

 Infection with Malaria occur in our Country ?] — Reprint from 

 Nederl. Tijdschr. voor Geneesk. [sine loco], Ixv, 1921, 2nd Half 

 no. 12, pp. 1485-1488. [Received 21st November 1921.] 



In the first part of this paper Dr. Korteweg states that the study of 

 malaria in Holland is simplified because only Plasmodium vivax and 

 Anopheles macidipennis are involved in practice, but that a complica- 

 tion is introduced by the difference in the habits of Anophelines in 

 town and country communities, especially as in the latter there are 

 many dykes, and stables and cowsheds are built among the dwellings. 



To ascertain the period when man is infected a distinction must be 

 made between primary cases and relapses. Children under one year 

 have a great degree of immunity. Investigations from 1903 to 1918 

 show that of 534 primary cases, 125 occurred before June. Koch has 

 suggested that primary cases in spring are due to the warm indoor 



