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5 is REPORT OF THE COMMISSIONER OF AGRICULTURE. 
In Some cases when the powers of life are much reduced and the © 
destruction of the lungs is far advanced, the same bacteria which are 
found entering the pleural cavity may appear in the blood, spleen, 
and other organs. This was true of No. 392, in which the chromo- 
gene there mentioned was found in the spleen as well as in the pleu- 
ral cavity. In a considerable percentage of the cases given, anaéro- 
bic bacilli were found in the cultures from the internal organs. These 
microbes may have gained entrance by way of the digestive tract 
(liver) or the diseased lings in the form of spores and developed un- 
der the peculiarly favorable conditions. Death usually takes place 
by a paralysis of the respiratory function (asphyxia); the right ven- 
tricle and large vessels are filled with large thrombi. The system 
being thus slowly but compietely deprived of its oxygen anaérobic 
bacteria may multiply and appear in cultures. They seem to be bu- 
tyric bacilli, judging from the odor emitted by the cultures. These 
bacilli carry on a feeble existence in the lowest strata of liquid cult- 
ures and die out very soon. 
The presence of the bacterium of swine plague in animals having 
hepatized lungs has been proved in several outbreaks, some of which 
have been dwelt upon in the preceding report of the Bureau. They 
may be summarized briefly as follows: The specific microbe was ob- 
tained from the spleen at Geneseo, Ill., July, 1886; from the pleural 
cavity (as a pure culture) of a pig at Sodorus, Ill., September, 1886; 
from lung tissue (by inoculation into rabbits) sent from Iowa, Jan- 
uary, 1887; from a considerable number of cases fully described in 
this report, studied at the experiment station of the Bureau during 
the winter of 1887. In all of these cases hepatization of the lungs 
was present. This organism has\ never been obtained in cultures 
from several hundred cases of hog cholera in which extensive lung 
disease was absent. 
The final proof of the causal relation between a given microbe and 
a disease having definite pathological characters can only be brought 
by actually reproducing the disease in healthy animals with pure 
cultures of the given microbe. 
In the experiments made with this in view, and detailed in the pre- 
ceding pages, cultures were introduced into the lungs through the 
trachea, and pigs were exposed to the spray of liquid cultures. In 
none of these experiments was the disease reproduced. In two cases, 
however, the injection of a few c. c. of culture liquid into the thorax 
produced large abcesses, the contained pus being of a semi-solid 
caseous consistence. The presence of the injected bacteria only in 
immense numbers proved them to be the cause of these changes. 
These two cases are by no means positive, but very presumptive evi- 
dence that the microbe under consideration is the true cause of swine 
plague. 
There are several reasons why this microbe may not produce the 
disease when introduced into the lungs by way of the trachea. There 
may be a rapid attenuation in artificial cultures. But more plausi- 
ble than this is the theory that in this, as in perhaps the great ma- 
jority of lung diseases, the specific bacteria can not gain a foothold 
unless there be some disease already existing which has been pro- 
duced by exposure or parasites, or both. It is a well-known fact that 
it is more difficult to produce diseases of a general character like an- 
thrax by introducing virus through the trachea into healthy lungs 
than by subcutaneous inoculation, as the air passages are well pro- 
vided with means for resisting the entrance of foreign particles, 
