THOUGHTS ON PLEUllO-PN liUMONIA IN CATTLE. 461 
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strangers to a brusli of any kind perhaps for thirty years, where 
there is no ingress nor egress for a breath of air, and where 
the manure heap is within one yard of the door, and only 
removed at rare intervals of time ; where the green, fetid, 
putrid, decomposing animal and vegetable matter is reeking 
and disgusting to the senses ; yet, strange as it may appear, the 
disease has never visited this loathsome place. From these facts 
I conclude that the germs of the disease are not equally dis¬ 
seminated in the air, but subjected to drifts or to some law not 
yet known to us. We have, I doubt not, each of us met with 
instances of this kind. How can this phenomenon be accounted 
for ? In the present state of our knowledge it is a mystery, 
but I think the influence is fairly deducible that this disease 
is not referable to any so-called nuisance, or any mephitic 
emanations. It runs its complete course unattended by the 
precise characteristics essential to true inflammation. But 
whilst this perplexing problem has been taxing my t brain 
there is one idea that has been fixing itself in my mind, and 
I find the conviction is growing stronger and stronger (and 
these discussions have only tended to incite my mind to more 
deep thought and study); it is this, that the disease is the 
direct action or effect of inhaling a special virus, an acrid 
pestilential malaria, which exists in the atmosphere; but 
whether it is a subtle geological elimination, an aerial poison 
chemically developed by certain favorable conditions of the 
atmosphere, or whether it be referable to the existence of some 
germinal spore or infusoria of infinitesimal minuteness in the 
air, are questions that science is not yet able to make known 
to us; we are only able to take cognizance of it by its effects. 
This acrid irritant comes into actual contact with, and becomes 
impacted upon the fine, delicate, sensitive membrane lining 
the air-cells. Of this I am persuaded, that a certain tangible, 
actual effect is produced upon it during the act of endosmosis 
and exosmosis. That thus this delicate membrane becomes 
impervious ; the effect being analogous to the action of some 
powerful caustic upon it, and therefore this membrane is the 
primary and special seat of the disease ; the interlobular struc¬ 
tures becoming implicated shortly afterwards. Occasionally 
we find the disease limited to clusters of lobules, or even to 
isolated lobules. If the atmosphere happens to be largely im¬ 
pregnated with this gas, or whatever else it may be, then the 
effect is sudden, causing instant serous effusion or exudation, 
and the whole substance of one or both lobes of the lungs 
swelling at the same moment; the symptoms become violent, 
and in a few hours the most inveterate, malignant tumefaction 
and induration is established, assuming very soon the gray or 
