Licence: In copyright
Credit: The prevention of malaria. Source: Wellcome Collection.
Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.
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![crescent curve may be very rapid and continuous. The fall may be equally rapid at first, but often alternates with short rises—suggesting continuous death and reproduction; but later the fall tends to be more gradual. Quinine (even in 2 gramme daily doses in a boy), soamine and methylene blue had no very decisive effect on the crescents when once formed. The crescents have never numbered more than 1/8 the highest number of sporids. Of the latter (malignant), 300,000 was the largest number found per c.mm. G. C. E. Simpson, working with us, has demonstrated parallel fluctuations of urobilin in urine and faeces. Faradic and galvanic currents applied to the spleen did not increase the number of crescents in the peripheral blood, and X-rays to the spleen did not prevent a relapse. (Compare Chapter IV.) The method gives at the same time much more accurate diagnosis, and is useful for obtaining the parasite rate (section 51). (4). S. T. Darling has recently done some good enumerative work at Panama, partly published [1909] and partly just communicated to me by letter [1910]. He counted the number of crescents in patients (by comparison with leucocytes), fed Anophelines on them, and then counted the zygotes in the insects; and estimates that the mortality of the parasites in the stomach cavity is 97% (section 18 (1)). A. albimana, bred in laboratory, weighed o'ooo8 grammes before feeding and oooi6 grammes after a moderate blood meal. He takes the average blood-meal to weigh about one milligramme, and from the number of gametids counted in the blood, he estimates the number which must have been ingested during the meal. This he compares with the number of zygotes actually found. For example, he estimated that one mosquito should have contained 1,632 zygotes after three feedings: but it contained only fifty. He thinks that fully half the ingested gametids are captured by leukids in the insect's stomach— as I showed in 1895. In one mosquito he found 168 zygotes. He concludes that if the gametids in a patient's blood are less than about 12 per c.mm. they will not be numerous enough to infect mosquitos. After experiments on a number of patients, he thinks that 30 grains of quinine taken daily will reduce the number of crescents (section 23). We have seen, however, that the crescent curve may fall quite irregularly, and sometimes vary rapidly, without any quinine. At my suggestion my brother, E. H. Ross, recently carried out the following experiments at Port Said, in parts from which mosquitos have been entirely banished: 344 Culex fatigans, males and females, 2 S](https://iiif.wellcomecollection.org/image/b21351600_0729.jp2/full/800%2C/0/default.jpg)
