PARALYSIS OF RADIAL NERVE. 775 



sometimes occurs after inflammation of its sheath, produces the 

 same disturbance in movement as paralysis. Section of the tendon 

 of the postea-spinatus results in precisely similar lameness. Dewar 

 has pointed out that the foregoing description of paralysis of the 

 suprascapular nerve is exactly applicable to the condition known 

 to horsemen in Scotland as " slipped shoulder," the most common 

 form of which is atrophy of the subspinatus muscle in three-year- 

 old horses being trained to agricultural work. The muscles of both 

 sides are often affected. As these animals work in traces, and have 

 not to back, the cause in their case can scarcely be a backward 

 movement of the shoulder. 



The disease may, of course, be accidentally complicated with 

 other injuries. Thus, in a riding-horse which had run away and 

 struck its shoulder against a tree, the levator humeri and pectoralis 

 transversus were ruptured and there was paralysis of the suprascapular 

 nerve. Rupture had probably occurred in other of the breast muscles. 

 Soon after the injury the hair fell away from a particular patch of 

 the skin and severe eczema developed. The longish oval patch, 

 which began about a hand's-breadth below the shoulder-joint, 

 extended perpendicularly upwards almost to the middle of the neck. 

 At the centre, and just over the shoulder-joint, it was about 8 inches 

 broad, and became smaller both in an upward and downward direction. 

 The hair which afterwards grew on the patch was of a lighter colour, 

 and if the animal was excited or slightly pushed sweating occurred 

 here, whilst all the rest of the body remained dry. The patch was also 

 insensitive to the prick of a needle. Without doubt this was a case 

 of simultaneous paralysis of the superficial scapular nerve. The 

 condition' improved, but very slowly. 



VII.— PARALYSIS OF THE RADIAL NERVE (PARALYSIS NERVI 

 RADIALIS). 



The radial (or musculo-spiral) nerve derives its fibres mainly from the 

 dorsal roots of the brachial plexus, but it also receives fibres from the 7th 

 and 8th cervical branches, and passes downwards and backwards on the 

 subscapularis and teres major muscles, and some little distance behind the 

 axillary vessels, from which it is separated by the ulnar nerve. On reaching 

 the deep humeral artery, it disappears in front of the large head of the 

 triceps, and is continued round the humerus in the musculo-spiral groove, 

 where it rests on the brachialis anticus, and afterwards, on the posterior 

 or outer border of that muscle. Before the nerve disappears behind the 

 humerus, it gives branches to the great and small heads of the triceps and 

 a long branch which passes backward to divide under the scapulo-ulnaris 

 for the supply of that muscle. Behind the limb it supplies the median 



