Pathology and Course of Chronic Roaring. 105 



July meeting at Newmarket, when she was probably unwell. 

 Immediately afterwards she was discovered to be a Roarer, 

 and continued so until the end of the following spring; 

 when it was found that the noise was gradually diminish- 

 ing, and it ultimately disappeared altogether, until at last 

 she was as sound as on the day she was foaled. After this 

 she won the Oaks, Ascot Gold Cup, and Hurstbourne Cup, 

 easily. 



In the first class of cases, the whole of the muscles of the 

 left side of the larynx (always excepting, of course, the 

 crico-thyroid) are usually involved throughout their entire 

 structure, and the process of degeneration goes on rapidly in 

 them. In the second class, these muscles are not wholly 

 affected, their innervation being only weakened or partially 

 suspended. For we may conclude, judging from the appear- 

 ances presented by the left abductor muscle and one or two 

 of the adductors, that individual fibres of the left recurrent 

 nerve have alone lost their conducting power, the remaining 

 fibres continuing to stimulate the portions of muscles to 

 which they send filaments. Consequently, a part of the 

 muscle may retain its irritability or contractile property, 

 while another part is paralysed. Cohen^ has remarked that 

 it is not known whether the double function of the recur- 

 rent nerve is due to innervation by a common centre, or 

 whether distinct centres preside over separate sets of fila- 

 ments ; while the influence which the pneumogastric nerve 

 may exercise upon abduction of the vocal cords as an 

 organic feature of the respiratory act, is a problem as yet 

 unsolved. 



In the third and somewhat rare class of cases, there is 

 only temporary derangement of the function of the recur- 

 rent nerve ; the suspension or modification not being suffi- 

 ciently prolonged to allow serious atrophy of the muscles 

 to take place. 



When the recurrent nerve becomes more or less incapable 



1 ' ' International Encyclopsedia of Surgery," p. 783. 



