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Nematode Pests

Nature volume 101, pages 9495 (04 April 1918) | Download Citation



PROF. WARRINGTON YORKE and Dr. B. Blacklock (in Annals of Trop. Med. and Parasitology, vol. xi., No. 2, 191.7) have recorded a series of interesting observations on the (periodicity of the larvæ of the nematode worm, Filaria bancrofti (nocturna), in an Australian who contracted the infection in Queensland. It is well known that during the night the larvæ of this species are concentrated in the cutaneous vessels, while during the day they are present there in small numbers only. The authors estimated the number of larvae in the cutaneous blood every two hours for a period of twenty-four hours on December 21–22, 1916, and again on January 5–6, 1917. The maximum concentration observed was at midnight, when there were 12,850 larvæ per cubic centimetre. Although the number of larvae fell to a low level during the daytime they were never absent, the minimum number, noted being 50 per c.c. of cutaneous blood. A discussion of the observations has led the authors to the conclusion that the nocturnal periodicity of the larvae is primarily dependent upon periodic variations in the arterial supply of larvæ to the cutaneous vessels. The periods of sleep

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