CHAPTER II. 



VARIOUS CAUSES OF NOISY RESPIRATION. 



Noisy respiration may be due to a variety of causes, as any 

 obstacle situated in the air-passages, and which interferes 

 with the free movement of the air to and fro in them, is 

 likely to give rise to an abnormal sound ; and there can be 

 no doubt that such sound, from whatever cause arisinsr, mav 

 be designated " Roaring," whether it is heard during inspira- 

 tion or expiration, or during both of these acts. In order to un- 

 derstand the pathology of the condition which we are specially 

 considering, and to distinguish it from the other sources of 

 noise- production, we will briefly notice some of these. 



Every horseman is, of course, familiar with the more or 

 less noisy breathing of horses out of training when they are 

 subjected to severe exertion ; the muscles of respiration, 

 and especially those of the upper air-passages, not being in 

 a state to dilate these sufiiciently, or to maintain them for 

 any length of time in a condition which will allow the in- 

 creased volume of air to pass freely to and fro. Fatigue of 

 these muscles invariably leads to this result. 



Very often, also, excitable horses will make a noise for a 

 short time when made to gallop, and particularly when the 

 head is held in a cramped position. Some horses, also, 

 which are not Roarers, are in the habit of making a noise 

 when pulling at the bridle in galloping, owing to their 

 opening the mouth and retracting the tongue so as to force 

 back the soft palate to such an extent that it interferes 

 with the passage of air between the nasal passages and the 

 larynx. So annoying is this noise sometimes to the rider, 



