298 DISEASES OP CATTLE. 



necessary to produce epizootic disease, namely : the predi* 

 posing cause which residas in the system, and the exciting 

 cause, which belongs to the atmosphere. Atmospheric 

 cause is being clearly proven from the fact of the early 

 symptoms of the disease being irritation of the mucous 

 membranes of the nostrils, nose, eyes, etc. That this may 

 be properly understood, let any person enter the too 

 frequently over-heated lecture room or theatre, with its 

 impure air, and on coming out to the keen air of night, 

 how readily the membranes of the eyes drop tears, and 

 sneezing from irritation of the nose takes place. Pleuro- 

 pneumonia being a disease chiefly attacking milch cows 

 and working oxen, and rarely affecting herds of cattle in 

 the field, we are carried back again in our inquiries to the 

 cow house, barn yard and its surroundings. There we 

 find the slop feed stimulating the cow to over secretion of 

 milk, and at the expense of her general health and condi- 

 tion — the smoking and putrefying dung heap — the imperfect 

 ventilation and over-heated stable — the giving of stimu- 

 lating feed, and immediately after turning the lieated 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, hoM'ever, if so, then they 

 cannot be the only exciting and predisposing causes of the 

 disease. 



Symptoms. As has been already stated, the early symp- 

 toms are irritation of the membranes of the nose, windpipe, 

 etc. The symptoms of this irritation are not perceived by 

 the farmer, till effusions of fluid are poured into the chest 

 in considerable quantities, interfering with the movements 

 of the lungs, and consequently the breathing or respiration: 



