62 STRONGYLIDiE OR PALISADE-WORMS. 



July. Strongylosis of the air-passages is generally observed 

 from March to October. They get into the throat and enter the 

 trachea ; here they burrow into the mucous membrane and form 

 lumps, which they quit at the end of the winter. The female 

 then gives rise to numbers of living young, hundreds of which 

 may be found in the mucous membrane of the lamb's throat. 

 The young develop partly in water or damp earth before they be- 

 come sexually mature. Sir George Brown says that in common 

 with other Strongyles they are swallowed by earthworms, and 

 again ejected after having gone through certain changes. Only 

 some of the hosts of embryos ejected can go through earth- 

 worms, however. He then suggests that some may become 

 parasitic in plants before they take up their abode in the warm- 

 blooded host. Filaria gives rise to vermiceous bronchitis. 



We find at least three other worms in the lungs of sheep — 

 namely, Pseudalis ovis-pulmonalis, a small coiled worm forming 

 tuberculous-like growths over and in the lung in which they 

 live ; and Hustrongylus rufescens and U. paradoxus, free in the 

 lung cavities, &c. "Whether there is any connection between 

 K rufescens and P. ovis-pulmonalis is not known : from what I 

 have observed I consider them quite distinct. E. rufescens 

 produces a kind of pneumonia. Two varieties of this disease 

 may be noticed — viz., (1) a lobular pneumonia produced by 

 adult worms in the bronchi, and (2) a diffuse pneumonia caused 

 by ova and embryos in the parenchyma of the lung. P. ovis- 

 pulmonalis produces a nodular pneumonia. Paradoxus is of 

 exceptional occurrence. 



The Armed Btrongyles of the Horse. 



Another large Palisade-worm, known as the Armed Palisade- 

 worm [Sclerostomum armatum) (fig. 20), is found in the lower 

 parts of the horse's gut, chiefly in the caecum and colon. It is 

 taken in by the horse in polluted drinking-water as a very min- 

 ute immature worm. This embryo bores into the blood-vessels. 



