THICK-WIND. 193 



sometimes interfering not at all with the health of the animal, that it is 

 Bcarcely worth while to persevere in any mode of treatment that is not 

 evidently attended with speedy benefit. The principal consideration to 

 induce us to meddle at all with chronic cough is the knowledge that horses 

 afflicted with it are more liable than others to be affected by changes of 

 temperature, and that inflammation of the lungs, or of the respiratory pas- 

 sages, often assumes in them a very alarming character; to which, perhaps, 

 we may add, that a horse with a chronic cough cannot legally or properly 

 be warranted sound. 



When chronic cough chiefly occurs after eating, the seat of the disease 

 is evidently in the substance of the lungs. The stomach, distended w.th 

 food, presses upon the diaphragm, and the diaphragm upon the lungs; ajjd 

 the lungs, already labouring under some congestion, are less capable of 

 transmitting the air. In the violent effort to discharge their function, 

 irritation is produced ; and the act of coughing is the consequence of that 

 irritation. This is allied with, or soon runs into. 



THICK-WIND. 



Tliick-wind consists in short, frequent, and laborious breathing, and 

 especially when the animal is in exercise ; the inspirations and expirations 

 often succeeding each other so rapidly as evidently to express distress, and 

 occasionally almost to threaten suffocation. Some degree of it frequently 

 exists in round-chested and fat horses, that have little or no breeding. The 

 reason of this is sufficiently plain. The circular chest affords sufficient 

 room for the expansion of the lungs when the animal is at rest, and suffi- 

 cient room for the accumulation of a great deal of fat and flesh ; but when 

 the horse is strongly exercised, the circulation of the blood is hurried, and 

 its change from arterial to venous, or from vital to empoisoned blood, is more 

 rapid. The circular chest cannot then enlarge to any great degree: yet the 

 blood must be purified in greater quantity, and therefore what cannot be 

 done by increase of surface, must be accomplished by frequency of action. 

 Heavy draught-horses are invariably thick-winded, and so are almost all 

 horses violently exercised on a full stomach. 



A horse labouring under any inflammatory affection of the lungs is thick- 

 winded, because the pain which he feels in the act of breathing will not 

 permit him to respire deeply, and therefore he must breathe quickly. A 

 horse unused to exercise is thick-winded, because the lungs will not soon 

 accommodate themselves to a new and laborious action. 



The principal cause, however, of thick-wind is previous inflammation, 

 and particularly inflammation of the bronchial passages. The throwing 

 out of some fluid, which is capable of coagulation, is the result, or the natural 

 termination of inflammation. This deposit in the substance of the lungs, 

 or in the bronchial tubes, from inflammation of these organs, must close 

 many of the air-cells, and lessen the dimensions of others. Then, if the 

 cells, fewer in number and contracted in size, be left for the purposes of 

 breathing, the rapid and laborious action of the lungs must supply the 

 deficiency, and especially when the animal is put in that state in which he 

 requires a rapid change of blood. 



The examination of thick-winded horses has thrown considerable light on 

 tlie nature of the disease. In the majority of instances, some of the small 

 air-cells have been found filled up with a dense substance of a blue or 

 da'-ker colour. In others, the minute passages leading to the cells have 

 been diminished, and almost obliterated, the linings of these passages being 

 unnaturally thickened, or covered with hardened mucus ^ and where 



