134 CAUSES OF UNSOUNDNESS. 



considerable diversity of opinion as to whether 

 " whistling " is a more advanced form of ^' roaring," 

 or whether it is the elementary stage of it. Both 

 "roaring" and ''whistling" constitute unsound- 

 ness, and detract from the pecuniary value of the 

 animal, though not necessarily from its utility. 

 Many hunters perform their work satisfactorily, 

 although they are what are termed '' rank roarers " 

 — a vulgar, but significant expression. A variety of 

 causes are capable of giving rise to both '' roaring " 

 and '' whistling," and it is only by a just apprecia- 

 tion of the causes operative in the production of 

 these abnormal respiratory sounds that one is en- 

 abled to form any opinion as to the duration of this 

 respiratory defect. It is, however, a most important 

 matter to be able to judge, or approximately esti- 

 mate, its duration. One of the — if not the — 

 commonest causes of this abnormal sound is that 

 arising through paralysis of certain muscles of 

 the larynx, the paralytic condition being due to 

 fatty degeneration of these muscles ; consequently, 

 they are no longer able to perform their normal 

 functions. Whether these changes are primary 

 or secondary is uncertain. But a branch of the . 

 left recurrent nerve supplies motive power to the 

 muscles diseased, so that this nerve is implicated 



