AS TO SOUNDNESS. 155 
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round the dorsal artery, which, as you know, is a small 
artery. On the left side the recurrent nerve leaves the 
pneumogastric very much further back, and turns round 
the posterior aorta, the largest of arteries. In doing so 
it bears the same relation to the artery that a sling bears 
to a lame arm, or, in other words, the artery is slung by 
the nerve. The artery, as you know, is constantly ex- 
panding and contracting, and so encroaching upon the 
nerve, which may or may not resist this, at all times, 
adverse influence. Where blood pressure is very great 
and prolonged it can seldom escape. If you wish to 
hear a typical roarer, you can do so almost at any time 
by going to Dr. George Balfour’s wards at the Infirmary, 
and listening to the breathing of poor creatures there 
with aortic aneurism. The nerve in some of these cases 
is almost pressed out to a ribbon shape. 
The noise takes place during inspiration—please. re- 
member that ; and it can be induced by frightening the 
horse into taking a sudden forced inspiration by the old 
custom of threatening him with a stick as he stands in 
his stall, or up against a wall. To.the practised ear the 
sound he then makes is unmistakable, whether it be a 
“roar” or a “grunt.” Warty growths on the vocal 
cords give rise to distressed breathing only when large. 
In this case a noise is heard at both inspiration and 
expiration. Tumours in the ventricles of the larynx are 
rare, but the same may be said of them as of those on 
the vocal cords. Chronic laryngitis is a very fruitful . 
source of mischief, as it is accompanied by thickening 
