CAUSES OF UNSOUNDNESS. 129 



what period may intervene between an attack and 

 the succeeding ones, but it may be months. 



Diseases affecting the Respiratory Organs. 



So far we have discussed some of the principal 

 diseases in relation to soundness affecting the sight 

 and the limbs, and although it is necessary that a 

 horse should be sound, or practically sound, in 

 sight and limb, it is even more desirable that it 

 should be sound in its wind. The following are 

 the principal diseases bearing upon the soundness, 

 or otherwise, of the horse. 



Broken Wind. 



Although a somewhat peculiar expression, the 

 term is a significant one, really meaning that the 

 respiratory act is broken or divided into two parts. 

 Normally, there is an inspiratory and expiratory 

 effort, or a taking in and breathing out of air. 

 In broken wind the inspiratory act is performed 

 normally, but the expiratory one is pecuUar, and 

 not performed as it ought to be — namely, by a 

 complete fall of the chest wall. It is divided into 

 two parts. The first portion of the act is suddenly 

 arrested, so that the remainder of the air within the 

 Jungs appears tQ be gradually squeezed out, and a 



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