448 SYMPTOMS OF DISEASE OF KESPIRATORY ORGANS. 



bear to a tube, orcranic or inorcranic, simijlv naiTowcd or 

 lessened in calibre, there appears no reasonable doubt. A 

 mistake, however, seems to be made in regarding the abnormal 

 noise as always dependent on the simple relative area or cali- 

 bre of the tube through which the air is forced, and neglecting 

 to consider whether the form of the tube or adventitious asperi- 

 ties, prominent angles, or other air-impeding entities, may not 

 possess some material influence in developing the pitch or 

 character of the sound. 



Although it is very difficult, if not impossible, in words ade- 

 quately and intelligibly to convey to the uninitiated a true 

 idea of the kind and character of these abnormal sounds, they 

 are, when heard for a few times, so impressed on the ear and 

 recollection that we rarely mistake them afterwards. A horse 

 that is very plethoric, and entirely out of work, will, when put 

 to rapid exertion, blow hard, the respiration will be accelerated, 

 and the animal may be distressed ; but the increased sound 

 in the respiratory act, by the rush of air along the air-tubes, is 

 in the key of health ; there is a softness and smoothness about 

 it, although rushing furiously along, which in disease we have 

 not : here the pitch is altered ; it is harsh, sonorous, wheezing, 

 or whistling. 



As a general rule, the unnatural sound is only heard 

 during the inspiratory part of the respiratory act ; instances 

 no doubt do occur where this is reversed, or in which it 

 is alike audible during both inspiration and expiration. In 

 very few cases will any noise of an abnormal character be 

 heard when the horse is at rest, or moving at a leisurely pace. 

 The greater number of horses of the lighter breeds do not, even 

 when made to exert themselves, emit a sound so distinctly roar- 

 ing, loud or harsh ; it is oftener of the character spoken of as 

 whisthng, a somewhat high-pitched and prolonged noise. In 

 the heavier breeds the unnatural sound is more sonorous, 

 harsh, and loud, ' roaring ' proper ; between these there are 

 variations depending on the seat of the inducing lesion, its 

 character, extent, and period of duration. 



E. The prohahle Seat of the Lesions connected with, or acting 

 as Factors in, the Production of the Unnatural Sound. — In 

 correctly determining the seat of the lesions which operate in 

 the production of this important symptom connected with the 



