anks; on a cold day one can see the condensation of the moisture
of the warm air as it comes from the lungs. The normal rate of
respiration for a healthy horse at rest is from 8 to 16 per minute. The
rate is faster in young animals than in old, and is increased by work,
hot weather, overfilling of the stomach, pregnancy, lying upon the side,
etc. Acceleration of the respiratory rate where no physiological cause
operates is due to a variety of conditions. Among these is fever;
restricted area of active lung tissue, from filling of portions of the
lungs with inflammatory exudate, as in pneumonia; compression of the
lungs or loss of elasticity; pain in the muscles controlling the
respiratory movements; excess of carbon dioxid in the blood; and
constriction of the air passages leading to the lungs.

Difficult or labored respiration is known as dyspnea. It occurs when it
is difficult, for any reason, for the animal to obtain the amount of
oxygen that it requires. This may be due to filling of the lungs, as in
pneumonia; to painful movements of the chest, as in rheumatism or
pleurisy; to tumors of the nose and paralysis of the throat, swellings
of the throat, foreign bodies, or weakness of the respiratory passages,
fluid in the chest cavity, adhesions between the lungs and chest walls,
loss of elasticity of the lungs, etc. Where the difficulty is great the
accessory muscles of respiration are brought into play. In great dyspnea
the horse stands with his front feet apart, with his neck straight out,
and his head extended upon his neck. The nostrils are widely dilated,
the face has an anxious expression, the eyeballs protrude, the
up-and-down motion of the larynx is aggravated, the amplitude of the
movement of the chest walls increased, and the flanks heave.

The expired air is of about the temperature of the body. It contains
considerable moisture, and it should come with equal force from each
nostril and should not have an unpleasant odor. If the stream of air
from one nostril is stronger than from the other, there is an indication
of an obstruction in a nasal chamber. If the air possesses a bad odor,
it is usually an indication of putrefaction of a tissue or secretion in
some part of the respiratory tract. A bad odor is found where there is
necrosis of the bone in the nasal passages or in chronic catarrh. An
ulcerating tumor of the nose or throat may cause the breath to have an
offensive odor. The most offensive breath occur