382 DISEASES OF BREATHINa. 



true that the majority of Arabs are under 14.2 ; but many of 

 the Indian country-breds, especially stud-breds, were over 15.2. 1 

 have known two or three instances of roarers, imported from 

 Australia into India, become perfectly sound in their wind, after a 

 residence of a year or two in that hot country ; a fact which shows 

 the strong influence of climate in this disease. It is evident that 

 such recovery is possible only during the early stages of roaring, 

 before any marked structural change has taken place in the affected 

 part (the larynx). Roaring affects about 5 per cent, of all the 

 horses in England. In Australia, probably not 1 per cent, of the 

 horses are wrong in their wind. In the United States, the 

 percentage is less than in this country. 



Although the fact of Ormonde being a roarer, was the apparent 

 cause of his not being retained in this country as a sire, it is 

 stated that none of the stock he sired in Argentina went wrong 

 in their wind. 



My experience in the interior of Russia convinces me that damp 

 greatly increases the predisposing influence which a cold climate 

 has on roaring. It has no effect in this respect, in the case of hot 

 climates. The same remark applies to the influence of climate in 

 producing coughs and colds. 



2. Heredity, especially in the dam, has a very strong predis- 

 posing influence in cold, damp climates, but an extremely Weak 

 one in hot countries. In India and South Africa the fact of a 

 dam or sire being " musical," was practically no detriment to his 

 breeding value. The only positive case of hereditary predisposition 

 in roaring I met with in India, was a thorough-bred two-year-old 

 colt whose dam, an Australian, was a roarer. On putting him into 

 work, I noticed that he made a noise, but he became perfectly 

 sound in his wind before he was three years old. 



The only proof of heredity being a cause of roaring is furnished 

 by some authorities who aver that they have met with cases in 

 which the left recurrent nerve was absent at birth. Such instances 

 are so rare, and have been so imperfectly authenticated, that a 

 predisposing influence may be regarded as the only part played 

 by heredity in the production of roaring. 



Breed, as a factor in roaring, comes under the heading of 

 heredity. Of all races of horses, the English thorough-bred is 

 most liable to acquire the paralytic form of roaring, a predis- 

 position more or less inherited by its descendants. The chief 

 reason for this characteristic liability is that this breed has 

 suffered during a long succession of years from causes best 

 calculated to establish a strong hereditary predisposition, namely : 

 residence in a cold, damp climate ; living, in many instances, in 

 heated and ill-ventilated stables ; being constantly fed on dry. 



