PLEURO-PNEUMONIA IN CATTLE. 
279 
Unhealthy air, expired by the sick and inhaled by the 
healthy, will often generate a general malady; and admit¬ 
ting any constitutional predisposition to exist in the animals, 
such contact must produce disease. The breath from putrid 
lungs cannot be inhaled with impunity. The cattle of which 
we are writing breathed into each other’s faces. Disease in 
the respiratory organs of the healthy was thus generated by 
the expirations, exhalations, and excretions of the sick. And 
if there was an insufficiency of pure air admitted into the 
building to counteract this deleterious ee miasma,” we have a 
sufficient and reasonable cause for the loss which has been 
sustained. 
I would farther remark, that much of the external air 
admitted into the cowhouse came from the cellar beneath it, 
by the frequent opening of the scuttles for the removal of the 
excretions of the animals ; this coming in upon their rear, and 
not in their front. Thus the foul air was near their nostrils, 
and because it was foul it impeded the admission of fresh air 
from the windows in the cowhouse, which probably were 
kept too frequently closed. 
I suppose that a current of fresh air from above will 
rest upon a stratum of foul air below, if the specific gravity 
of the last be greater. And it must be greater because it is 
charged with the moisture of the fermentation of the manure 
below and the excretions of the animals within. I would 
here observe, that in regard to ventilation, the owner was ex¬ 
tremely desirous to secure pure air in the cowhouse, and in 
the building of it impressed as much as possible on the 
minds of the mechanics its necessity. He had from twelve 
to fourteen windows on the east, south, and west sides, and 
also an opening in the roof, and the bottoms of the windows 
were about four feet from the floor. 1 lence a difficulty, as I 
have before described, in properly ventilating the building. 
Again, as the owner only visited the animals for about an 
hour each day, and that in the afternoon, he was not present 
at the closing or opening of the cowhouse, consequently he 
could not know the mode of ventilation, or if any existed. 
Since his loss, the owner has had the cowhouse thoroughly 
cleansed and purified, and its ventilation improved by 
openings made through the walls, upon the surface of the 
floor, and by a funnel introducing pure air from without 
through a large grating in its centre, by which means pure 
air is now diffused over the whole floor, the foul escaping 
from a large ventilator through the roof, since which all 
sickness has entirely disappeared. 
The whole number of cattle lost is twenty-seven. 
