Pathology and Course of Chroydc Roaring. 103 



become much augmented in size and deeper in colour, they 

 having undergone a kind of compensatory hypertrophy in 

 the efforts to perform the work of their vanished fellows. 



It may be remarked that the changes which the atrophied 

 muscles of the larynx undergo are simply those observed in 

 other muscles as a result of prolonged inactivity, especially 

 due to loss of nerve-stimulus {neuropathic origin of 

 atrophy). 



That the atrophy is owing to defection of the left recur- 

 rent nerve, and not to disease of the muscles themselves 

 (myopathic origin), is supported by the strongest evidence. 

 In the first place, if chronic Roaring were occasioned by 

 myopathic paralysis, we should find proof of it in the 

 appearance of the muscles, and particularly if it were due 

 to inflammation in them ; one of the results of this would 

 be an increase of the fibril sheaths (perymisium), such as is 

 observed in chronic myositis. And, in the second place, we 

 should not have the muscles of the left side of the larynx 

 alone involved in nearly every case of Roaring, and those on 

 the right side not only perfectly healthy, but unusually 

 developed. 



In cases of long-existing chronic Roaring, the left recur- 

 rent nerve and its filaments have become so wasted, that 

 little is left of them except their sheath ; and this, even, is 

 so attenuated that a most careful dissection is required to 

 find it : a circumstance that has led some investigators to 

 the conclusion that the nerve was congenitally absent. Of 

 course, this is not the case. Like the muscles, this nerve 

 undergoes, after a certain time, such degenerative changes 

 as other nerves are liable to from various causes ; the nerve- 

 sheath, then the axis-cylinder, becoming atrophied and 

 altered, the white substance of Schwann being sometimes 

 increased ; this change is coincident with a lighter colour of 

 the nerve, and diminution in its circumference, until it is 

 completely Avasted. 



This implication of the nerve in the morbid changes has 



