mp out this
contagion, and, except Holland, it was the first to reach success.

_The cause (etiology) of pleuropneumonia._--This is a contagious disease,
and arises only by contagion from a previously affected animal;
consequently it can never be seen here except as the result of importing
affected animals from the Old World. When thoroughly stamped out it does
not reappear; and if imported animals continue to be properly inspected and
quarantined, we have every reason to believe that pleuropneumonia will
never again be seen in this country.

The exact nature of the virus or contagion of lung plague has never been
determined. Various investigators have from time to time claimed the
discovery of the specific organism of the disease, but it was not until
1898 that Nocard and Roux, by an ingenious method of cultivation, succeeded
in obtaining a very feeble growth of an exceedingly minute microorganism.
With these cultures the disease was produced in cattle.

Some investigators and writers are of the opinion that the disease can be
contracted only by an animal coming near enough to a living diseased one to
receive the contagion directly from it. They hold that the contagion is
expired with the air from the affected lungs, and that it must be almost
immediately inspired by another animal in order to produce the disease.
Some experimental attempts to infect animals by placing them in stables
where diseased animals have been, and by placing the diseased lungs of
slaughtered animals in their feeding troughs have failed, and,
consequently, apparently confirm this view.

* * * * *

CONTAGIOUS PLEUROPNEUMONIA.
DESCRIPTION OF PLATES.

PLATE XXIX. Upper or dorsal surface of the lungs of the ox, reduced to
one-twelfth of the natural size: _a_, _a'_, the right and left principal
lobes. These are the largest and are situated posteriorly, resting upon
the diaphragm; _b_, _b'_, the ventral lobes, situated between the principal
lobes; and _c_, _c'_, _c''_ the most anterior, or cephalic, lobes. The
right anterior is divided into two lobes (_c_, _c'_), the left is single
(_c''_); _d_, trachea, or windpipe.

In the majority of the lungs examined in the laboratory of the bureau which
were affected with contagious pleuropneumonia the principal lobes (_a_,
_a'_) were primarily affected.

PLATE XXX. Bronchopneumonia. The ventral or middle lobe of the right lung
affected with collapse and beginning bronchopne