dly
marbled appearance. Again, in traumatic pneumonia, caused, as its name
implies, by the entrance of foreign bodies into the lung tissue, generally
from the paunch, the connective tissue around the place of disease becomes
inflamed and thickened, and the disease itself may simulate pleuropneumonia
in its retrogressive stages when it is confined to a small portion of lung
tissue. The filling up of the interlobular spaces with fibrin and
connective tissue of inflammatory origin is not thus limited to
pleuropneumonia, but may appear in a marked degree in other lung diseases.
It must not be inferred from this statement that these interlobular changes
are necessarily the same as those in pleuropneumonia, although to the naked
eye they may appear the same. We simply note their presence without
discussing their nature.

In general, the distinction between pleuropneumonia and bronchopneumonia is
not difficult to make. In the latter disease the pneumonia generally
invades certain lobes. The disease attacks the smaller lobes in their
lowest portions first and gradually extends upward, i. e., toward the root
of the lung or the back of the animal and backward into the large principal
lobes. Again, both lungs in advanced cases are often symmetrically
affected. In contagious pleuropneumonia the large principal lobe of one
side is most frequently affected, and a symmetrical disease of both lungs
is very rare, if, in fact, it has ever been observed. The lung tissue in
bronchopneumonia is not enlarged, but rather more contracted than the
normal tissue around it. This is well illustrated in Plate XXX. Normal,
air-containing lobules may be scattered among and around the hepatized
portion in an irregular manner. In pleuropneumonia the diseased and healthy
portions are either sharply divided off, one from the other, or else they
shade into each other by intermediate stages.

The hepatized lung tissue in bronchopneumonia when the cut surface is
examined is visually of a more or less dark flesh color with paler
grayish-yellow dots regularly interspersed, giving it a peculiar, mottled
appearance. In the more advanced stages it becomes more firm, and may
contain nodular and firmer masses disseminated through it. The air tubes
usually contain more or less soft, creamy, or cheesy pus or a turbid fluid
quite different from the loose, fibrinous casts of acute pleuropneumonia.
The interlobular tissue may or may not be affected. It sometimes contai