OUE DOMESTICATED ANIMALS. 113 



their tails ; but it would "seem that before they finally 

 gain access to the horse they must enter the body of 

 some intermediary bearer, and finally be swallowed by 

 the ultimate host along with drink or green fodder. 



In all likelihood their next active wanderings are the 

 immediate cause of the formation of the aneurisms, from 

 whence, by means of a very complicated mouth-arma- 



Fig. 26. Palisadb Worms in a Blood Vessel. 



ture, acting like a file and trephine, they subse- 

 quently bore their way into the intestinal canal, in which 

 situation they at length acquire full growth and sexual 

 maturity. 



As this worm belongs to the dung-feeding division of 

 the nematodes, there is no difficulty in recognising with 

 the naked eye through the transparent skin the dark- 

 coloured contents of the intestine. In the female parasite 

 this excrementitious matter sometimes forms little pellets 

 or masses incrusted around the anal aperture ; and these 



I 



