d to
determine the various pathological changes that occur in the respiratory
organs. Auscultation is the act of listening, and may be either mediate or
immediate. Mediate auscultation is accomplished by aid of an instrument
known as the stethoscope, one extremity of which is applied to the ear and
the other to the chest of the animal. In immediate auscultation the ear is
applied directly to the part. Immediate auscultation will answer in a large
majority of cases. Auscultation is resorted to in cardiac and certain
abdominal diseases, but it is mainly employed for determining the condition
of the lungs and air passages. Animals can not give the various phases of
respiration, as can the patients of the human practitioner. The organs
themselves are less accessible than in man, owing to the greater bulk of
tissue surrounding them and the pectoral position of the fore extremities,
all of which render it more difficult in determining pathological
conditions. (See Pl. VIII.)

The air going in and out of the lungs makes a certain soft, rustling sound,
known as the vesicular murmur, which can be heard distinctly in a healthy
state of the animal, especially upon inspiration. Exercise accelerates the
rate of respiration and intensifies this sound. The vesicular murmur is
heard only where the lung contains air and its function is active. The
vesicular murmur is weakened as inflammatory infiltration takes place and
when the lungs are compressed by fluids in the thoracic cavity, and
disappears when the lung becomes solidified in pneumonia or the chest
cavity filled with fluid as in hydrothorax. The bronchial murmur is a
harsh, blowing sound, heard in normal conditions by applying the ear over
the lower part of the trachea, and may be heard to a limited extent in the
anterior portions of the lungs after severe exercise. The bronchial murmur
when heard over other portions of the lungs generally signifies that the
lung tissue has become more or less solidified or that fluid has collected
in the chest cavity.

Other sounds, known as mucous rales, are heard in the lungs in pneumonia
after the solidified parts begin to break down at the end of the disease
and in bronchitis where there is an excess of secretion, as well as in
other conditions. Mucous rales are of a gargling or bubbling nature. They
are caused by air rushing through tubes containing secretions or pus. They
are said to be large or small as they are distinct or indistinct, de