THE EXAMINATION OF A SICK HORSE. 19 
mothorax, there is an excess of air in the chest cavity, the percussion 
sound becomes abnormally loud and clear. 
Auscultation consists in the examination of the lungs with the ear 
applied closely to the chest wall. As the air goes in and out of the 
_lungs a certain soft sound is made which can be heard distinctly, 
especially upon inspiration. This sound is intensified by anything 
that accelerates the rate of respiration, such as exercise. This soft, 
rustling sound is known as vesicular murmur, and wherever it is 
heard it signifies that the lung contains air and is functionally active. 
The vesicular murmur is weakened when there is an inflammatory 
infiltration of the lung tissue or when the lungs are compressed by 
fluid in the chest cavity. The vesicular murmur disappears when air 
is excluded by the accumulation of inflammatory product, as in pneu- 
monia, and when the lungs are compressed by fluid in the chest 
cavity. The vesicular murmur becomes rough and harsh in the early 
stages of inflammation of the lungs, and this is often the first sign of 
the beginning of pneumonia.. 
By applying the ear over the lower part of the windpipe in front of 
the breastbone a somewhat harsh, blowing sound may be heard. This 
is known as the bronchial murmur and is heard in normal conditions 
near the lower part of the trachea and to a limited extent in the ante- 
rior portions of the lungs after sharp exercise. When the bronchial 
murmur is heard over other portions of the lungs, it may signify that 
the lungs are more or less solidified by disease and the blowing bron- 
chial murmur is transmitted through this solid lung to the ear from a 
distant part of the chest. The bronchial murmur in an abnormal 
place signifies that there exists pneumonia or that the lungs are com- 
pressed by fluid in the chest cavity. 
Additional sounds are heard in the lungs i in some diseased condi- 
tions. For example, when fluid collects in the air passages and the 
air is forced through it or is caused to pass through tubes containing 
secretions or pus. Such sounds are of a gurgling or bubbling nature 
and are known as mucous rales. Mucous rales are spoken of as being 
large or small as they are distinct or indistinct, depending upon the 
quantity of fluid that is present and the size of the tube in which this 
sound is produced. Mucous rales occur in pneumonia after the solid- 
ified parts begin to break down at the end of the disease. They occur 
in bronchitis and in tuberculosis, where there is an excess of secretion. 
Sometimes a shrill sound is heard, like the note of a whistle, fife, or 
flute. This is due to a dry constriction of the bronchial tubes and it 
is heard in chronic bronchitis and in tuberculosis. 
A friction sound is heard in pleurisy. This is due to the rubbing 
together of roughened surfaces, and the sound produced is similar 
to a dry rubbing sound that is caused by rubbing the hands together 
or by rubbing upon each other two dry, rough pieces of leather. 
