PREVENTION, SYMPTOMS AND TREATMENT ,c 



way to include chronic dyspnea in horses, dogs, cattle and other 

 animals arising from various causes. In this sense it is merely a 

 symptom of chronic heart lesions, emphysema and chronic bron- 

 chitis, obstructive lesions in the upper air passages, paralysis of the 

 left recurrent laryngeal nerve, chronic renal disease, etc. It is often 

 confused with asthma, but this term should be limited to a distinct 

 functional nervous disorder (neurosis) appearing in severe attacks 

 of intense dyspnea — often when the patient is asleep or at rest — 

 with prolonged, labored, wheezy expiration, small pulse and cold 

 extremities. When suffocation seems imminent the fit passes away, 

 often with cough. In the intervals respiration is apt to be somewhat 

 difficult and wheezy. Such is true of bronchial asthma and this is 

 rarely seen in the larger animals, but occasionally in dogs. True 

 asthma is due either to spasm or sudden swelling and congestion of 

 the bronchioles — very likely to both. It is induced by irritation of a 

 medullary center through afferent impulses conveyed from the 

 bronchi (irritation by dust, etc.), from the stomach and intestines 

 (indigestion), from the nose (dust, smoke, irritation and obstruc- 

 tion by polypi, hypertrophic conditions, etc.), ear and genital 

 organs. Persistent asthmatic attacks lead to distension of the 

 pulmonary alveoli and emphysema, with disturbance of circulation 

 in the lungs, and therefore chronic bronchitis. In the horse, over- 

 exertion after a time not infrequently causes emphysema and em- 

 physema commonly occurs in the horse in broken wind. It is diffi- 

 cult to know, then, whether broken wind in the horse is caused by 

 emphysema or is of a neurotic origin from indigestion, or both. 

 Broken wind is, however, often induced in horses by overloading of 

 the digestive organs with poor, coarse hay, and the dust of hay (as 

 in man) may also incite it through irritation of the nasal or bron- 

 chial mucous membrane. This form of broken wind is therefore 

 akin to asthma and due to irritation of the vagus endings in the 

 stomach. Dyspnea is more frequent in these cases after eating 



Digitized by Microsoft® 



