STEONGYLIDJJ OR PALISADE- WORMS. 69 



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 become 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 earthworms, 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 Strongylus rufescens and S. paradoxals, free in the 

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

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

 I have observed I consider them quite distinct. 8. 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 produced a nodular pneumonia. S. paradoxus is of 

 exceptional occurrence. 



Stomach Worms of Sheep) and Cattle. 



Several species of Strongylidse often occur in enormous 

 numbers in the stomach of sheep and cattle and cause parasitic 

 gastritis. One of the commonest is the Hcemonchus contortus of 

 sheep, which also infests cattle and goats. Lambs are specially 

 infected. This worm occurs in the abomasum or fourth stomach. 



