NEMATODA TRICHOTRACHELIDAE 



145 



Trichocephalus dispar Eud. (hominis G-mel.) is common in 

 man, and also occurs in 

 some species of monkey. 

 It does not live freely 

 within the intestine, but 

 buries its long whip-like 

 anterior end in the mucous 

 lining of the caecum or 

 colon. The eggs pass out 

 of the body of the host. 

 The development of the 

 embryo is slow, lasting 

 many months ; whilst still 

 in the egg-shell the em- 

 bryos are swallowed, and 

 give rise to the sexually- 

 mature parasite without 

 the intervention of an 

 intermediate host. They 

 are by no means uncom- 

 mon. Davaine calculated 

 that about 50 per cent of 

 the inhabitants of Paris 

 were infested with them, 

 but they give rise to little disturbance, and only very occasionally 

 cause serious harm. T. affinis Eud. infests sheep ; T. crenatus 

 Eud. the pig ; T. depressiusculus Eud. the dog ; and T. ungui- 

 cidatus Eud. the hare and rabbit. 



The genus Trichosoma, with many species, is as a rule found 

 in birds, but it occurs also in mammals, as T. plica Eud. in the 

 bladder of the fox and wolf, T. felis cati in the bladder of the 

 cat, T. aerophilum Duj. in the trachea of the fox and marten. 

 The chief interest of this genus is that, at any rate in T. 

 crassicauda Bel., which infests the rat, the dwarf males live two, 

 three, or four at a time within the uterus of the female, a con- 

 dition of things which recalls the similar arrangement found in 

 the G-ephyrean Bonellia. 



Trichina spiralis is the cause of the well-known disease 

 trichinosis, which appears in two forms, intestinal and muscular, 

 according to the habitat of the -parasite. The mature forms of 



L 



Fig. 71. 



-Trichocephalus dispar Rud., attached to 

 part of the human colon, x 2. 



5 to the habitat of the parasite. 



VOL. II 



