Causes of Chronic Roaring. 123 



defect after Strangles in all likelihood ' depends upon 

 whether the tracheal and bronchial glands — between which 

 and the submaxillary glands there is great sympathy — are 

 inflamed and swollen. 



It has long been known that Eoaring often follows the 

 above diseases, though its cause was not suspected. Sixty 

 years ago, Professor Sewell, of the Royal Veterinary College, 

 wrote, in reference to it : " When it takes place in colts that 

 have not been broken or regularly domesticated, it is 

 usually the result of severe cases of Strangles that have not 

 terminated favourablj^, but left a thickening, and often 

 chronic ulceration, of the mucous membrane lining the 

 larynx ; in others it is preceded by severe colds and sore 

 throats, producing similar lesions of structure. The latter 

 is frequently the cause in all kinds of horses, and in all 

 unhealthy seasons, in spring especially, the disease has its 

 origin." ^ 



The occurrence of Roaring in young horses which have 

 never done any severe work — in fact, no work at all — such 

 as army remounts, but which have suffered from Strangles 

 and fevers implicating the chest and its contents, militates 

 against the development theory of the defect, and also that 

 of nerve stretching by the posterior aorta. 



Whether a high temperature will cause disturbance in 

 the function of the left recurrent nerve in horses unaccus- 

 tomed to it, cannot be decided ; but it is most probable that 

 there were, in the instances recorded of English horses be- 

 coming Roarers in hot climates, antecedent or collateral 

 causes in operation which were overlooked, but which were 

 more potent than this : such as fever on board ship, with 

 congestion of the lungs and pleurse, exhaustion, etc. 

 Spooner-Hart ascribes the cases of Roaring observed 

 among imported horses at Calcutta, to the elevated tem- 

 perature of the summer, which induces what he terms 

 " thermic fever." ■' A patient, after an attack of such high 

 1 " The Veterinarian," 1829, p. 68. 



