Asthma. Broken Wind. Heaves. Dyspnoea, Etc. 371 



stomacli often causes broken-wind and nothing will more surely 

 aggravate it, when it does exist. The same remark may be made 

 of the drinking of large quantities of water after feeding and just 

 before going to work. Gross feeders are above all others the sub- 

 jects of the complaint. 



The question arises how a disturbing cause, operating directly 

 upon the digestive organs, should affect the jespiratory, in such a 

 marked and permanent manner. It cannot be because of the 

 gastric and abdominal distension since pregnant mares, though in 

 a state of much greater plenitude, are not thereby rendered 

 liable to broken wind, and if they have previously suffered from 

 this infirmity, the symptoms are usually less marked when breed- 

 ing. The explanation first advanced by Dupuy appears to be the 

 correct one. The lungs, the stomach, and certain other organs 

 derive innervation from the vagus nerve, and certain disturbances 

 of the stomach and intestines so impair the function of this nerve 

 that the lungs are affected, at first functionally and afterwards 

 structurally. In support of this view is the fact that broken 

 wind is usually associated quite as much with digestive as respira- 

 tory derangement. The horse though a heavy feeder becomes 

 unthrifty, hidebound and emaciated ; his dung is passed in an 

 undigested state like so much chopped straw, and flatus is con- 

 tinually passed from the bowels. Indeed the almost incessant 

 passage of wind and faeces, during the first mile or two of a jour- 

 ney, is a disgusting evidence of the malady. The power of 

 doses of shot, fat and other agents to temporarily allay the symp- 

 toms may be held to point in the same direction. 



Beside causes operating on the side of the digestive organs 

 others undoubtedly superinduce the disease, and among these, se- 

 vere exertions and chronic bronchitis ought to hold prominent 

 positions. 



Over-exertion induces over-distension and rupture of the air cells 

 by the forced retention of air within the lungs, by the closure of 

 the glottis, while the chest is strongly compressed by the respira- 

 tory muscles. It is an essential condition to all severe exertion 

 in man that the breath should be held, and though the horse ap- 

 pears equal to the same efforts of draught after the operation of 

 tracheotomy has deprived him of the power of holding the breath, 

 yet he would seem to be sooner exhausted (Goubaux, Colin, 



