THE RESPIRATOEY APPAEATUS. 321 



always remarkably laboured in this disease. It will be ob- 

 served, however, on autopsy ^ that little exudation into the 

 air-passages has taken place, and that, though the mucous 

 membrane is purple, it has not undergone such an amount 

 of change as a- ^Wori might have been anticipated. This is 

 attributable to the fact that the irritant is a living one, 

 capable of altering its position, and simply occupying its na- 

 tural habitat. When the lungs of an animal which has been 

 affected with this disorder, but has recovered, are examined, 

 it will be found that the worms have become encysted, and 

 have undergone calcareous degeneration, forming nodular 

 calcareous deposits in the lungs. The average duration 

 of an attack is two or three weeks. 



Treatment. — Though we are not assured of all the 

 phases in the life history of Strongylus micrurus, we know 

 that when ova are expelled from the lungs on to pastures 

 they undergo changes which are dependent upon warmth 

 and moisture in some way or other, and result in the 

 assumption by the immature parasite of the state in 

 which it is fit to gain entry into the alimentary canal with 

 food or water. It remains for some little time in the 

 primao viae, and then becomes comparatively inaccessible. 



Preventiorij therefore, consists in housing all severely 

 affected animals, and destruction of bedding materials and 

 other matters on which the discharges from the patients 

 fall; removal of all the slightly diseased to high and dry 

 pastures, giving them a judicious supply of water not 

 liable to be contaminated, and rock salt; feeding them 

 liberally with strengthening diet and administering doses 

 of iron tonics which are anthelmintic. With regard to 

 the housed animals they must be treated with stimulant 

 tonics and carefully nursed. Williams has seen excellent 

 results from administration of prussic acid, which allays 

 bronchial irritation and destroys the worms, but most 

 authorities seem to prefer more energetic treatment with 

 a view to actual expulsion of the parasites. Thus, tur- 

 pentine is much lauded, since it is excreted to a certain 

 extent through the bronchial mucous membrane, and is 

 supposed to render their habitat uncomfortable to the para- 



21 



