226 CLINICAL DIAGNOSTICS. 



when they return to the normal (the number counted before 

 exercising). 



In healthy horses the number of respirations 

 runs as high as 50 or 70 per minute, sometimes even higher. 

 Respiration occurs without exertion, the animals may now and 

 then give a voluntary snort and take a few deep inspirations. 

 In the course of at most 15 to 18 minutes after cessation of 

 the exercise, the number of respirations should be reduced to 

 that observed at rest. 



"Heavey" horses, on the other hand, show increased 

 or difficult breathing, dyspnea (see p. 99 J. Inspiration and 

 expiration may be so difficult that the number is not increased, 

 but the character of the respiratory movements enables us to 

 recognize the dyspnea. But as a rule the number of res- 

 pirations, when animals are exercised as above described, runs 

 up to 80 to 120 per minute and goes back to the normal very 

 gradually. Not infrequently this requires 30 to GO minutes. 

 In chronic bronchitis a white foamy nasal discharge is ob- 

 served. 



III. Examination for Roaring. 



The term "roaring" is applied to a form of breathing 

 attended with the production of an audible sound and due to 

 a chronic, incurable disease of the larynx or trachea. 



As a rule, roaring is caused by a paralysis of the 

 left recurrent nerve and the resulting inactivity and degener- 

 ation of the muscles which it supplies (Hemiplegia laryngis 

 sinistra). 



In rare cases a paralysis of the right recurrent nerve or 

 a bilateral paralysis may exist; sometimes thickening of the 

 mucous membrane or the presence of tumors may be the cause. 

 An exact diagnosis of the cause of such a stenosis can be defi- 

 nitely determined only with the aid of the laryngoscope; but 

 in 99 per cent, of all cases a left handed paralysis is the cause. 



Except in rare cases, laryngeal roaring is no- 



