158 'INFINITE TORMENT OF FLIES' 



actively wriggle and coil and uncoil their bodies, their 

 progress is as small and their struggles as little 

 effective as are those of a man in a strait-waistcoat. 



The causes of the periodicity of the appearance of 

 these round-worms in the superficial bloodvessels are 

 not completely understood, but they appear to have 

 more relation with the usual sleeping hours of 

 humanity than with day and night. In individuals 

 who sleep by day and work by night the Filaria 

 nocturna is found in the bloodvessels of the skin 

 during the day. Thus, whilst between 5 p.m. and 

 7 or 8 a.m. the vessels of the skin of Cox the Hatter 

 would be well peopled by the round-worms, they 

 would only come to the surface in Box the Printer 

 during the daytime, whilst he was sleeping in the 

 lodgings of Mrs. Bouncer. 



One reason of the normal appearance of the 

 creatures in the blood at night is undoubtedly con- 

 nected with the habits of its second host, the gnat or 

 mosquito. Two species are accused of carrying the 

 Filaria from man to man Culex fatigans and Anopheles 

 nigerrimus. Sucked up with the blood, the round- 

 worms pass into the stomach of the insect. Here they 

 appear to become violently excited, and rush from one 

 end to the other of their enveloping sheath, until they 

 succeed in breaking through it. When free, they 

 pierce the walls of the stomach of the mosquito, and 

 come to rest in the great thoracic muscles. Here the 

 Filarias rest for some two or three weeks, growing 

 considerably, and developing a mouth and alimentary 

 canal; thence, when they are sufficiently developed, 

 they make their way to the proboscis of the mosquito. 

 Here they lie in couples, and it would be interesting 

 to determine whether these couples are male and 

 female. Exactly how they effect their exit from the 

 mosquito and their entrance into man has not yet been 

 accurately observed, but presumably it is during the 



