468 SPORADIC DISEASES. 



been found much enlarged, and containing masses of dry food 

 adherent to its walls. 



In some districts the disease prevails, or used to prevail, to a 

 great extent. In some parts of Wales I have very frequently 

 noticed many broken-winded horses ; and upon inquiry, have 

 discovered that their fodder has been of the worst possible 

 description. I quite agree with Professor Gamgee that broken 

 wind is at first a purely nervous affection, dependent on the 

 condition of the digestive system, and in which the pneumo- 

 gastric nerve is especially involved, and that the organic lesions 

 are the effects of the nervous disorder. Some horses are 

 peculiarly prone to suffer from broken wind, where no fault 

 can be detected in the method of feeding. Such animals are 

 constitutionally predisposed to indigestion, tympany, and irregu- 

 larity of the bowels ; they are generally round, shallow-chested 

 horses, but are not bad thrivers before they become affected 

 in the wind. 



Fatliology. — The smaller air tubes are surrounded by in- 

 voluntary muscular tissues ; in broken wind, owing to the 

 irritation of the par vagum, the function of this muscle is inter- 

 fered with. In the early stages, and during the paroxysms of 

 broken wind, it is spasmodically contracted ; in the later stages 

 most probably it is paralyzed ; in either condition there is 

 arrest of respiration. The irritation arises from the action of 

 indigestible food upon the cardiac branches of the vagus, and 

 is reflected to the pulmonary branches of the same nerves. 

 Eecent experiments by Bert have convinced him that the lungs 

 contract under the influence of the vagus, branches of which, it 

 will be remembered, supply both the lungs and stomach, as well 

 as other organs. The action of the bronchial muscle surround- 

 ing the tubes is brought into play during the expiratory move- 

 ment, whereby the lungs are assisted in expelling the tidal air. 

 The same thing happens in the lungs of a horse suffering from 

 broken wind as in the lungs of a human being suffering from 

 asthma. Owing to nervous irritation, there is arrest of respira- 

 tion, and this can occur either in expiration or in inspiration ; 

 the arrest during expiration being the more easily induced, 

 indeed " in some animals it is impossible to obtain arrest during 

 inspiration." — (Paul Bert.) The arrest takes place in the act 

 (inspiratory or expiratory) which happens to be going on at 



