FILARIA BANCROFTI 289 



in Queensland by Bancroft, and soon after Lewis found it in Calcutta ; 

 it was described by Cobbold as Filaria bancrofti. The male was first seen 

 by Bourne in 1888. 



The lymphatic vessels of various parts of the body of man 

 are doubtless the normal habitat of the ADULT WORMS, but these 

 have also been found in the left ventricle of the heart. The 

 females are viviparous, but exceptionally they also deposit eggs ; 

 the young larvae, by means of the lymph stream, reach the blood, 

 and are distributed with it throughout the body ; they also pass 

 through the blood vessels, and may be found in the secretions of 

 glands, such as the lachrymal and Meibom's glands, kidneys, &c. 

 The manner of appearance in the peripheral circulation, which 

 has been particularly studied by Manson, is peculiar : the larvae 

 are first seen in patients, the blood specimens of which have been 

 taken after sunset. Their number then increases considerably until 

 about midnight, and after begins to diminish ; from midday until the 

 evening no filariae are found in the peripheral b)ood. The cause 

 of this peculiarity cannot be explained, as was conjectured, by a 

 periodical production of larvae, because the cycle can be reversed. 

 If the patients are made to sleep in the day-time and remain 

 awake at night, the filariae appear in the day-time and disappear 

 at night. The manner of appearance, therefore, is connected with 

 sleep, and depends on the fact (v. Linstow) that during sleep the 

 peripheral cutaneous vessels are somewhat dilated, but during the 

 waking hours are contracted ; the filariae cannot pass through the 

 contracted capillary system, but remain in the larger trunks in 

 the depth of the cutis. 1 



[The night swarming of the larvae of F. bancrofti in the peripheral 

 circulation is correlated with the life-habits of its liberating agent. 

 We can find a large number of similar remarkable correlations in 

 Nature. Many flowers which open early in the morning are only 

 visited by particular butterflies which leave their nocturnal haunts 

 at the same hour ; other flowers do not open till sunset, and they 

 are visited by hawk-moths, silk-moths, owlet-moths and other 

 Noctuse, which commence their ramblings when dusk sets in. 



Then again, the development of flower scent is simultaneous with 



1 Manson was able to examine the body of a man who died from poisoning at 

 8.30 a.m. During life the filariae had appeared regularly in the blood from 6 p.m. to 

 8 a.m. They were entirely absent from the peripheral circulation, but were found 

 in the large vessels, particularly in the arteries ; further, in the capillaries of the brain 

 and of the voluntary muscles, in the vessels of the kidneys and the heart. The largest 

 numbers were present in the pulmonary vessels. Manson does not accept v. Linstow's 

 explanation, but is of opinion that the products of metabolism of a waking person 

 drives the filariae from the periphery or attracts them to the interior (Manson, P., 

 " On Filarial Periodicity," Brit. Med. Journ., London, 1899, ii., p. 644). 



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