16 DISEASES OF THE HORSE. 
and above this point it is regarded as very high. In some diseases, 
such as tetanus or sunstroke, the temperature goes as high as 108° or 
110°. In the ordinary infectious diseases it does not often exceed 
106°. A temperature of 107.5° and above is very dangerous and must 
be reduced promptly if the horse is to be saved. 
THE ORGANS OF RESPIRATION. 
In examining this system of organs and their functions it is cus- 
tomary to begin by noting the frequency of the respiratory move- 
ments. This point can be determined by observing the motions of 
the nostrils or of the flanks; on a cold day one can see the condensa- 
tion 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, »verfilling of the stomach, preg- 
nancy, lying upon the side, etc. Acceleration of the respiratory rate 
where no physiological cause ope’ . ° ‘> to a variety of condi- 
tions. Among these is fever; restricted area o1 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 1 7s of respiration are brought 
into play. In great dyspnea thé . ‘ % -ands 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 ex- 
pression, the eyeballs protrude, the up-and-down motion of the 
larnyx 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 con- 
tains 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 
