18 DISEASES OF THE HOESE. 



rate of respiration for a healthy horse at rest is from 8 to 16 per min- 

 ute. 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 por- 

 tions of the lungs with inflammatory exudate, as in pneumonia ; com- 

 pression of the lungs or loss of elasticity; pain in the muscles con- 

 trolling the respiratory movements; excess of carbon dioxide 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 rheu- 

 matism 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 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 in- 

 dication 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 occurs 

 where there is necrosis, or gangrene, of the lungs. 



In some diseases there is a discharge from the nose. In order to 

 determine the significance of the discharge it should be examined 

 closely. One should ascertain whether it comes from one or both 

 nostrils. If but from one nostril, it probably originates in the head. 

 The color should be noted. A thin, watery discharge may be com- 

 posed of serum, and it occurs in the earlier stages of coryza, or nasal 

 catarrh. An opalescent, slightly tinted discharge is composed of 

 mucus and indicates a little more severe irritation. If the discharge 

 is sticky and pus-like, a deeper difficulty or more advanced irritation 



