PLEURO-PNEUMONIA. 343 



various chancres in the condition of the weather, without 

 producing the disease, something being wanted in the 

 animal economy to act as a predisposing cause, thus 

 two causes being necessary to produce epizootic disease, 

 namely : the predisposing cause which resides in the sys- 

 tem, and the exciting cause, which belongs to the atmos- 

 phere. Atmospheric cause is being clearly proven from 

 the fact of the early symptoms of the disease being irri- 

 tation of the mucous membranes of the nostrils, nose, 

 eyes, etc. That this may be properly understood, let 

 any person entei' the too frequently over heated lecture 

 room or theatre, with its impure air, and on coming out 

 to the keen air of night, how the membranes of the eyes 

 drop tears, and sneezing from irritation of the nose takes 

 place. Pleuro-pneumonia being a disease chiefly attack- 

 ing milch cows and working oxen, rarely affecting herds 

 of cattle in the field'; thus we are carried back again in 

 our inquiries to the cow house, barn yard and its sur- 

 roundings — the slop feed stimulating the cow to over 

 secretion of milk, and at the expense of her general 

 health and condition — the smoking and putrefying dung 

 heap — the imperfect ventilation and over-heated stable — 

 giving of stimulating feed, and immediately after turning 

 the heated cow out to the cold, and sometimes frozen 

 watering trough, to quench her thirst. In one or other 

 of these anomalies or all combined, will be found the 

 cause of this epizootic disease. Contagion, if it is really 

 contagious, which I honestly doubt and even deny, how- 

 ever, if it is contagion then it cannot be the only exciting 

 and predisposing cause of the disease. 



Symp>toms. — As has been already stated, the early 

 symptoms are irritation of the membranes of the nose, 

 windpipe, etc. The symptoms of this irritation are not 



