452 SYMPTOMS OF DISEASE OF EESPIRATOIIY ORGANS. 



4. Lesions connected with the Trachea. — The changes which, 

 in the great air-tube, seem to result in the production of 

 this unnatural respiratory sound are — (a) Changes of form or 

 calibre, the result of injury, or disease of the naturally resist- 

 ing walls by which its integrity, as a perfect air-conduit, is 

 interfered with ; (b) Textural changes connected with the lining 

 membrane, as morbid growths, or the partial organization of 

 inflammatory products ; (c) Distortion and change of form pro- 

 duced by pressure from without, acting much as in the case of 

 meclianical injury, by causing change of area or lumen in the 

 air-tube. 



Mode of Detecting this Abnormal Condition or Sound. — Proceed- 

 ing upon the knowledge that the unnatural sound is often 

 elicited without putting the horse to any very severe exertion, 

 that the essential condition connected with its production is to 

 induce a sudden and rapid passage of air along the air- tubes, 

 the method of startling the animal by placing him against a 

 wall, and making a feint to strike him, is adopted, and generally 

 with success in those animals where the lesion, upon which the 

 abnormal sound depends, is fully established. Pressure with 

 the fingers over the body of the larynx, inducing coughing, 

 will also assist us in judging of the condition of this part of 

 the air-tube. Should these methods of testing yield affirma- 

 tive evidence of the abnormal state of the respiration, it may, 

 when very patent, not be needful to proceed further. In the 

 greater number of instances, however, we find it necessary to 

 put the animal to some severe or rapid exertion, by which the 

 respiratory movements will require to be called into vigorous 

 and prolonged action. In draught-horses this is very readily 

 attained by causing them to drag a good load, at a brisk pace, 

 up an incline, which, if they are able to accomplish without 

 emitting an abnormal noise, the respiratory function may be 

 considered as in fairly good condition. 



The same end may be attained, though we do not think so 

 rapidly nor so unmistakably, with both draught-horses and 

 the lighter breeds, by simply causing them to move rapidly, 

 usually at the gallop, for a few hundred yards past the 

 examiner ; this is the ordinary method of examining all 

 horses, while, with animals broken for saddle use, it is the 

 only practicable one. 



