362 



UTILITARIAN ZOOLOGY 



Dog and Rabbit (or Hare) are the two hosts of another kind 

 of Tape- Worm [Tcenia serrata), of which the adult Hves in the 

 intestine of the former animal, while the bladder-worm stage 

 (Cysticercus pisifo^nnis) is harboured in the body of the latter. 



Injurious Thread- Worms (Nemathelmia). — Many of the 

 worms belonging to this group are injurious to domesticated 

 animals and cultivated plants. The large Horse- Worm (Ascaris 

 megalocephala), for example, often infests in great numbers the 



intestine of the horse and its 

 allies, while smaller species of 

 round -worm live as parasites 

 within clogs and cats. Much 

 more daneerous is the minute 

 Trichina {Trichina spiralis) 

 that sets up trichinosis in pig 

 and man (see p. 343). 



Much harm is caused by 

 the Palisade-Worms or Stron- 

 gyles {Strougylidcs), related 

 to the species which produces 

 "miners' anaemia" in human 

 beings (see p. 343). The 

 Giant - Strongyle {Eustron- 

 gylns gigas), of which the 

 female may be from a foot 

 to over a yard long, lives in 

 the kidneys of horse, ox, 

 dog, and, it may be, man. 

 Swellings in the arteries of 

 the horse are caused by the 

 presence of Armed Strongyles {Stroiigyhis arinatits\ while other 

 deadly parasites are the Stomach - Strongyle {S. contortiis) of 

 the sheep, and the Lung- Worm (5. filaria) of the lamb. The 

 disease known as "gapes", to which young poultry and game- 

 birds are liable, is caused by the presence of a related species, the 

 Red- or Forked- Worm {Syngavius trachcalis). 



Some of the little Eel- Worms [Augiti/Zii/idtT) are serious agri- 

 cultural pests. They possess a spine at the front end of the body, 

 by which they bore into the tissues of plants. One species, the 

 Wheat Eel-Worm {Tylenchus scandens), has been described in 



Fig. 125S. — The Tape- Worm [Ti.cuia cwnuras), of which 

 the cyst causes "staggers" In Sheep, i, parts of the adult 

 worm [a, head; d^, ripe joints) ; 2, head of same { X 30) show- 

 ing hooks and suckers; 3, cyst from sheep's brain. Several 

 groups of developing tape-worm heads are indicated. 



