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that the salivary medium of the mosquito cannot be regarded as the 

 true hibernating medium of malarial sporozoites, which may remain 

 for months in the salivary glands without being ejected because 

 no meal of blood is taken. The role of winter host of the malarial 

 parasite devolves upon man. 



This paper concludes with a discussion on the subject of the presence 

 of Anophelines without malaria and the danger of the spread of malaria, 

 in France. Experience has justified, in principle, the fears expressed 

 by several writers of the spread of malaria in France as a consequence 

 of the War. Isolated cases of infection and even slight epidemics of 

 locally-acquired malaria have been notified from various parts of 

 France ; generally the infection was due to P. vivax, but in some 

 cases P. fraecox was equally the cause. There is therefore some ground 

 for the fear that the tropical tertian form may become established in 

 France. The author does not think such a contingency likely to 

 occur. He points out that the three factors necessary for the dis- 

 semination of the disease, namely, man, the virus and the Anopheline 

 carrier, are not in themselves sufficient to give rise to endemicity ; 

 a further necessary condition is the establishment of frequent and 

 continuous relations between man who is the reservoir of the virus 

 and the local Anophelines. Temporary or exceptional relations 

 between the two hosts break the continuity of the cycle and tend 

 to suspend the endemicity, which can only be established when the 

 mosquitos become domesticated and appear constantly in human 

 habitations. The author points out the analogy of these conditions, 

 with those he has described as essential for the endemicity of human 

 trypanosomiasis in Africa ; sleeping sickness is not rife wherever 

 Glossina palpalis and possible carriers of trypanosomes occur ; the 

 endemicity is established preferably where tsetse-flies live permanently 

 at the exclusive expense of man in the absence or scarcity of other 

 hosts capable of furnishing their nourishment. 



The conditions producing such close relations between man and 

 Anophehnes in France are as yet but little understood. Attention 

 has previously been drawn to the scarcity of A. maculi'pennis in the 

 houses around Paris and in the valley of the Essonne, a region where 

 malaria is absent, in contrast to their relative abundance in the houses 

 of the villages and boroughs of Vendee, where endemic malaria is 

 rife. The fact is that in the French chmate the local Anophelines 

 are not markedly blood-suckers ; this is important, since it 

 furnishes a logical explanation of the much-discussed problem of 

 their presence in the absence of malaria. The author is decidedly 

 not of the opinion, expressed by some writers, that in non-malarial 

 regions the Anophehnes have lost the habit of biting man. Observa- 

 tions have led him to the conclusion that A. maadipennis, and doubtless 

 A. bifurcat'us also, do not take chance flights even at a short distance 

 from their breeding-places for the purpose of finding nourishment 

 in houses, but that they have definite and constant zones of flight,, 

 within which they travel in search of any suitable source of nourish- 

 ment, whilst outside these zones their attacks are not to be feared.. 

 The extent of these zones of flight varies according to exterior conditions 

 and the facihties for obtaining meals of blood. The same observations 

 have been made in the case of the Anophelines of the Panama Canal; 

 Zone. The ideal conditions for intimate relations between man and 



