DISEASES OF THE RESPIRATORY ORGANS. 133 



hard. Soft whistling occurs in acute laryngitis, when 

 there is considerable increase of mucus, and also when the 

 mucous membrane is temporarily swollen. If it be 

 occasioned by a large amount of mucous secretion, it is of 

 a wheezing character, and is mostly diminished when the 

 horse coughs. If it arises from inflammatory infiltration 

 of the laryngeal mucous membrane, it is louder during 

 inspiration than in expiration. 



Soft Whistling constitutes temporary unsoundness, and 

 it is, in many cases, unsafe to hazard a decided opinion 

 for some days or even weeks, until the thickening of the 

 mucous membrane and relaxation of the vocal cords has had 

 time to subside. 



Dry Whistling. — According to some authorities, dry 

 whistling is to be regarded as a modified form of roaring. 

 Others, however, are of opinion that whistling and roaring 

 are due to difi'erent pathological conditions of the larynx, 

 and that they may exist independently of each other. 

 With the latter views we entirely concur. 



Dry whistling, like roaring, is a noise made more espe- 

 cially during inspiration. It is due to diminished calibre of 

 the larynx, and sometimes of the trachea, owing to per- 

 manent thickening of the mucous membrane, distortion of 

 the neck by tight reining, the presence of a tumour in the 

 trachea, or to any cause which diminishes the calibre of 

 the passages through which the air passes to and from the 

 lungs. 



Whistling, though loudest in inspiration, is by no means 

 always absent during expiration. 



If entirely absent during expiration, the pathological 

 change is to be sought in the larynx, or upper part of the 

 air-passages. 



Whistling, like roaring, is often traceable to hereditary 

 taint, and constitutes unsoundness. 



