WHISTLING AND EOARING. 447 



B. If it has developed gradually ajxcrt from any apprecioMe 

 Ca use. — Ordinarily this is the condition or history which is pre- 

 sented to ns of the unnatural sound, whether arising from 

 lesions of the nasal chambers, or in connection with the 

 laryngeal or tracheal portions of the air-tube. 



G. Whether it exists at all times ivhen the Animal is placed 

 under similar Conditions, or only occasionally. 



D. Its particular Quality and the Conditions under tvhich 

 it is produced, both during Inspiration and Expiration. — This 

 question of character or quality is an important one. There 

 are many who regard all these abnormal sounds heard during 

 exertion as merely indicative of a more or less aggravated 

 condition of the same disease. In this light ' roaring ' is 

 looked at merely as an advanced state or more severe form of 

 ' whistling.' 



Others, again, regard the character of the sound emitted 

 during exertion as entirely determined by the calibre of the 

 tube through which the air is passed, and consequently view the 

 higher-pitched and shriller note as evidence of a smaller laryn- 

 geal opening, and therefore that an animal which whistles is 

 exhibiting a more advanced stage of the condition formerly 

 recognised as roaring. 



In actual practice, however, we meet with many instances of 

 horses which are what is universally recognised as ' whistlers ' 

 which have not passed through the stage of ' roaring ;' and 

 many so-caUed ' roarers ' which have steadily advanced from 

 one degree of roaring to another, without ultimately terminat- 

 ing as whistlers. 



Mr. Percival, than whom there was no more acute or correct 

 observer, seems to have entertained the latter opinion, viz., that 

 the high-pitched sound was the more advanced state. He 

 says, reasoning from certain experiments which he made by 

 means of a ligature passed around the trachea of a horse: 

 ' That a certain diminution of the calibre of the air-tube pro- 

 duces roaring ; that further diminution or contraction of its 

 area causes whistling. A whistler, therefore, I regard as an 

 intense roarer : a wheezer, I should say, is something short of 

 an actual roarer.' 



Of the truth of these results, as far as the nature or character 

 of the sounds elicited, and the relation which these wiU 



