AS TO SOUNDNESS. 



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 itispiration — please re- 

 member that j 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 



