516 REPORT OF THE COMMISSIONER OF AGRICULTURE. 
usually round, rarely irregularly elongated. They are occasionally 
present in such numbers that the affected lobe feels like a bag filled 
with small marbles. It is highly probable that now and then the 
pathologic process may go a step farther. The caseous mass may be 
separated by secondary suppurative processes from the living tissue, 
soften, and be discharged through a bronchus, leaving an irregular 
cavity. We have seen but once what appeared to be cavities in a 
piece of lung sent to us from the west. 
A few lungs have come to our notice in which this process of slow 
necrosis was not limited to groups of a few or more lobules, but had 
involved the entire lobe uniformly. The tissue was completely air- 
less and bloodless, of a homogeneous consistency, cutting tike cheese, 
yellowish, with a semi-translucent, waxy luster. ; 
In distinction from the acute type of this disease, the process end- 
ing in caseation may be regarded as essentially slow and chronic, It 
may either be due to a diminished virulence of the bacteria or to a 
greater resistance on the part of the lung tissue. The former suppo- 
sition seems to us nearer the truth, and there is much other evidence 
which points to a rapid attenuation of this specific virus. 
The pathological process may be briefly summarized as follows: 
The bacteria, which have somehow entered the air tubes, begin their 
destructive activity in the alveoli and ultimate bronchi. A copious 
exudate, consisting chiefly of desquamated epithelium and round 
cells or leucocytes, fills them completely. Although the bacteria are 
finally destroyed by the exudate, the latter impairs by pressure the 
nutrition of the lung tissue proper, and the whole becomes involved 
in necrosis. The covering of the lungs is secondarily affected. In 
acute cases the pleura of the hepatized lobes may be covered with a 
fibrinous exudate of a spongy texture, containing a considerable num- 
ber of round cells and bacteria. It may become several millimeters 
thick, and tends to unite the lungs with the chest wall. The adhe- 
sion is at first broken without injury to the lung substance and is 
quite easily peeled from the pleura itself, as shown in Plate I. Not 
infrequently the diaphragm is more or less firmly glued to the base 
of the principal lobe when that is diseased, as is shown in Plate IT. 
The pulmonary pleura and adherent costal pleura may sometimes 
form cavities between them, containing a yellowish-white, very tur- 
bid liquid crowded with bacteria. The adhesions are sometimes very 
close, the costal pleura having its minute vessels much injected at 
such spots. In older cases there are bands of fibers, of various 
lengths and density, bringing about the adhesion. In most cases the 
pleuritis is dry, with no adhesions. Over the dead lung tissue the 
leura may be opaque and thickened or quite transparent, as in 
health. In several cases in which gangrenous processes were indi- 
cated by putrid odors, a generalized pleurisy was found gluing the 
entire lungs to the chest wall by means of a pasty exudate. In this 
various bacteria were found, which, very likely, had a share in the 
inflammatory changes. The pericardium occasionally is involved 
with the pleura and is subject to similar changes. In but one of the 
cases (No. 366) thus far examined was the epicardium covered with 
a fibrinous exudate. 
Intestinal lesions.—In the severe types of this disease, there are 
very extensive lesions of the large intestine. These on superficial 
examination resemble those of hog cholera so much that this sim1i- 
larity alone may have prevented the separation of these two diseases 
by pathologists who have studied them very carefully. 
