105 



Lagriffoul (A.) & PicARD (F.). Mode d' Action du Climat sur la Reparti- 

 tion g6ographique du Paludisme, [Influence of Climate on the 

 Geographical Distribution of Malaria. ]^BwZZ. Soc. Path. Exot., 

 Paris, xi, no. 2, 13th February 1918, pp. 73-80. 



The authors, continuing the discussion regarding the influence of 

 climate on malaria [see this Review, Ser. B, vi, p. 81], remark upon 

 the scarcity of mixed infections observed by them. The fact that 

 Plasmodium praecox alone is found in the tropical zone, and that 

 this form of malaria does not exist in France, while in the sub-tropical 

 zone the two and even the three forms are found, appears to the 

 authors to be simply explained. P. praecox requires a high temperature 

 for its development in the mosquito. The conditions essential to its 

 development are present in the tropical zone practically all the year 

 round. In the Mediterranean region, on the contrary, P. praecox is 

 at the limit of its habitat ; it is only from July onwards that it finds 

 conditions favourable for its existence. It is remarked, however, 

 that this form can produce autumnal infestation, the oocysts, which 

 require a very high temperature in order to reach maturity, having 

 then produced sporozoits that can live a long time in lower tempera- 

 tures. There is therefore an intermediate season when the mosquito 

 continues to carry infection, but is no longer caj)able of becoming 

 itself infected. But P. praecox never occasions a spring infestation, 

 because the needs of the oocyst with regard to temperature are no 

 longer satisfied, or only very rarely and very locally ; this species 

 cannot therefore maintain its existence. P. vivax, on the contrary, 

 can develop in the Anopheline in a moderate temperature. It there- 

 fore accompanies P. praecox in the tropical zone, carries infection 

 from the springtime onward in the Mediterranean region and will 

 continue its existence alone further north, where it becomes aestivo- 

 dutumnal, as is P. praecox in the South. 



The authors are of opinion that man can carry the crescent form of 

 the parasite for a long time in France, even in winter, and cite several 

 cases that have come under their observation. With regard to the 

 rapid disappearance of P. praecox, it is pointed out that carriers of 

 this form are treated in Dr. Vaillant's model dispensary with three 

 quinine doses a week, while cases parasitised by P. vivax are only 

 given quinine after positive microscopic examination ; it is thought 

 that this may explain the rapid disappearance of the one form and 

 the persistence of the other. This is not considered as refuting the 

 theory that the varying constituents of the liquid environment of the 

 parasite play an important part in the control of malaria [loc. cit.]. 



The authors consider it dangerous to assume that carriers of the 

 crescent form of the parasite become rapidly and spontaneously cured 

 in France. These persons are capable of creating centres of infection 

 around them, and in the south of France at least P. praecox might 

 become established in this way. 



M. Marchoux, in the discussion aroused by this paper, limited 

 himself to the statement of a few positive and established facts, 

 remarking that he has himself known cases of tertian malignant infec- 

 tion become cured spontaneously in France upon recovering a good 

 general state of health. In an organism living at a constant tempera- 

 ture the interior environment is essentially variable in its reactions. 



(C473) Wt. P2/137. 1,500. 6.18. B.&F.,Ltd. Gp. 11/3. a 



