Symptoms and Diagnosis of Chronic Roaring. 65 



inspiration may be prolonged to twice, or even thrice, the 

 normal period during severe and continuous exertion. It 

 is obvious, therefore, that in the quickened respiration 

 necessitated by this exertion, which always requires a cor- 

 responding increase in the quantity of air taken into the 

 lungs, when the obstacle to its admission is considerable, 

 the horse must suffer to a corresponding degree— mentally 

 and physically'; and the distress occasioned by the hesoin 

 de respirer accentuates the physical effects of the deficiency, 

 causing the horse — no matter how courageous — to " stop as 

 if shot," or, in more common parlance, to '' shut up " sud- 

 denly, when asphyxia is imminent. 



This disturbance in the respiratory rhythm is, like the 

 noise, not manifested when the horse is in a tranquil state ; 

 but when the Roaring commences it then becomes evident, 

 and as the dyspnoea increases the animaPs physiognomy 

 betrays the amount of distress he experiences. When this 

 is great, all the inspiratory muscles are most energetically, 

 indeed spasmodically, active in endeavouring to overcome 

 the laryngeal stenosis, in order to inflate the lungs to their 

 fullest dimensions. The expansion of the thorax, wide and 

 free at first, appears to become less and less with each inspi- 

 ratory eflbrt ; the loins rise and fall ; the nostrils are like the 

 mouth of a speaking-trumpet, through their extreme ex- 

 pansion involving their appendages — the false nostrils — 

 their special muscles (the inspiratory levatores aim nasi) 

 standing boldly out in their rigid contraction : for without 

 this muscular aid the nostrils would tend to close, because 

 of the rapid rarefaction or exhaustion of air in the nasal 

 cavities. Expiration is comparatively easy and rapid, and this 

 disproportion in the force required in the two acts constitutes 

 the peculiar characteristic of the dyspnoea which marks 

 cases of advanced Roaring ; hurried respiration is by no 

 means characteristic of it. In pulmonary emphysema, or 

 " broken wind," as it is commonly termed, the converse is the 

 case. It is the very essence of the self-acting function of 



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