into the air passages and lungs are the traumatic causes of pneumonia.

_The symptoms_ vary in the different forms of pneumonia. In case pneumonia
occurs secondarily, the earliest symptoms are confounded with those of the
primary disease. The first symptoms noticed may be a high body temperature,
as indicated by chills, and refusing to eat. The visible mucous membranes
are red and congested, the nostrils dilated, the respirations quickened and
difficult, the expired air hot and the pulse beats accelerated. The animal
coughs, and in the horse, a rusty discharge may be noticed adhering to the
margins of the nostrils. The horse refuses to lie down if both lungs are
inflamed. In severe cases the expression of the face indicates pain, the
respirations are labored, the general symptoms aggravated, and the animal
stands with the front feet spread apart. Cattle are inclined to lie down,
unless the lungs are seriously affected. Hogs like to burrow under the
litter.

_The course of croupous pneumonia_ is typical, and unless it terminates
fatally in the first stage, the periods of congestion, hepatization and
resolution follow each other in regular manner. Auscultation of the lungs
is of great value in diagnosing and watching the progress of the disease.
It is more difficult to determine the character of the lung sounds in the
horse and cow than it is in the small animals. This is especially difficult
if the animal is fat. During the period of _congestion_ which lasts about a
day, one can hear both healthy and crepitating sounds. The period of
_hepatization_ is characterized by an absence of sound over the diseased
area. The inflammatory exudates become organized at the beginning of this
stage, and the air can not enter the air cells. This period lasts several
days. _Resolution_ marks the beginning of recovery or convalescence. Toward
the end of the second period, the inflammatory exudate in the air cells has
begun to degenerate. In the last stage, these exudates undergo liquefaction