510 



HEALTH AND DISEASE 



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Roaring and Whistling. Koaring and whistling are defects of 

 respiration, arising out of a diseased condition of some portion of the 

 air- passages, whereby one or the other of these sounds is produced, 

 according to the nature and degree of the obstruction. As usually met 

 with, it is a chronic and incurable disease, resulting from paralysis of 

 the dilator muscles of the larynx. Less frequently it arises from other 



causes of a temporary character. 



Causes. Perhaps no equine affec- 

 tion has attracted more attention from 

 veterinary authorities than this, and 

 the opinion is universally held by them 

 that in a large measure heredity is re- 

 sponsible for its wide prevalence. 

 Most people, whether interested in 

 horses or not, have had the subject 

 forced upon their attention from time 

 to time in connection with turf cele- 

 brities, and if the hereditary character 

 of roaring had been more generally 

 accepted in the early days of horse- 

 racing there is no doubt that both our 

 thoroughbred stock and their half-bred 

 produce would have been less subject 

 to the malady than they are now known 

 to be. So many celebrated roarers 

 have gone to the stud that persons 

 best acquainted with the stud-book 

 tell us it is difficult to find a thorough- 

 bred horse whose progeny are abso- 

 lutely free of roarers. Be this as it 

 may, the race-horse of to-day is so 

 susceptible that the slightest cough in a favourite animal spreads dismay 

 among owners and trainers, and a large section of the general public 

 not unfrequently share in the alarm. Chronic roaring is generally 

 referable to wasting of the dilator muscles of the larynx, following upon 

 a cold, an attack of influenza, or strangles, or some affection of the chest, 

 all of which appear to have the effect of causing paralysis of the nerve 

 of supply to the parts affected; or it may, and does, come about while an 

 animal is in the best of general health. Numerous dissections prove that 

 the left side of the larynx is almost invariably diseased, and the theory is 

 suggested that this nerve (the left recurrent branch of the pneumogastric) 



Fig. 207. Larynx of a " Roarer" 



A, Thyro-arytenoid Cartilage. B, Arytenoid 

 Muscle. c, Crico-arytenoid Muscle. D, Left 

 Arytenoid Muscle (atrophied). E, Left Crico- 

 arytenoid Muscle (atrophied). 



