362 



UTILITARIAN ZOOLOGY 



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

 of Tape- Worm (Ttenia serrata), of which the adult lives in the 

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

 (Cysticercus pisiformis} 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 dogs and cats. Much 

 more dangerous 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- 



Q IVy j^au^^u^ gyles (Strongylidce), related 



L Jj'j fj| to the species which produces 



Eui P" /sZ^ \A\fSm "miners' anaemia" in human 



H ffl I fit beings (see p. 343). The 



Giant - Strongyle (Eustron- 

 gylus 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 (Strongylus armatus), while other 

 deadly parasites are the Stomach - Strongyle (S. contortus] of 

 the sheep, and the Lung- Worm (S. 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 (Syngamus trachealis). 



Some of the little Eel- Worms (Anguillulidce] 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. 1258. The Tape- Worm (Tcenia ccenurus), of which 

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

 worm (a, head; bb, 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. 



