102 Roaring in Horses. 



mucous and submucous tissues), polypi, and other altera- 

 tions mentioned in a preceding chapter. These conditions 

 the veterinary surgeon who determines on operation for 

 the removal of Roaring should be prepared for, though 

 they are so extremely unusual. 



The gross appearances which I have described as char- 

 acteristic of the morbid changes found in the larynges of 

 horses which were Roarers, belong to an advanced stage. 

 In this the muscles of the left side, with the exception of 

 the one which has a different nerve-supply, are wasted, but 

 the dilator or abductor muscle shows this more markedly 

 than the constrictors. 



At an early stage, before the Roaring is very pronounced 

 or continuous, the left dilator appears to be alone affected ; 

 its colour being paler — the paleness being in proportion 

 to the wasting of the muscle-substance, which leaves the 

 sheath of this more apparent — and its texture softer than 

 that of the right muscle. 



In this condition, there is only weakness {paresis) of the 

 left dilator muscle. At a more advanced stage, this muscle 

 has lost much of its convexity, is softer and paler, and 

 there are yellowish streaks of fatty tissue among its fibres, 

 especially towards its inner border — fat granules or cells 

 having taken the place of the muscle-substance. The con- 

 strictors on the same side now begin to manifest a similar, 

 though less advanced, change, and the left arytsenoid carti- 

 lage is on a lower level than the right. In some instances, 

 the dilator muscle is unequally involved in atrophy, the 

 change being limited to one or more portions of its substance, 

 the outer border of the muscle being evidently the last to 

 undergo degeneration. The constrictors are certainly the 

 last to suffer seriously. 



The degenerative process may cease at any stage, or pass 

 on rapidly to the final one, in which all the muscle-sub- 

 stance of the affected muscles has disappeared ; while the 

 corresponding muscles of the right side appear to have 



