518 
PARALYSIS OF RADIAL NERVE. 
ear over the scapula while this manipulation is performed by an assistant 
crepitation may be detected. 
Not infrequently paralysis is partial. The greater number of cases 
seen by Moller in the summer of 1887, and certain cases observed later, 
were distinguished by the fact that the function of the caput medium 
(M. anconeus extern us) and of the extensors lying in the region of the 
fore arm was clearly retained, whilst the other portions of the caput 
muscle appeared relaxed; when weight was placed on the foot, these 
contracted in the usual way. For this reason the lameness has a pecu¬ 
liar character: during the period when weight is placed on it, and at the 
moment when the limb is perpendicular, the shoulder is suddenly jerked 
forwards; the scapula and humerus move with a visible jerk, causing the 
disease to present a certain similarity to suprascapular lameness. But as 
these involuntary movements take place in a forward direction (best seen 
by moving the horse slowly and viewing it from the side), the disease is 
readily distinguished from the above lameness, where the shoulder moves 
directly outwards (see “Paralysis of the Suprascapular Nerve”). The 
condition is characterised by “ supporting leg lameness” and jerking of 
the shoulder forwards at the moment when the limb is upright. 
The reason of the caput medium being sometimes unaffected in this 
lameness must be sought in the distribution of the nerves. From the 
point of origin twigs are first given off for the heads of the caput 
magnum muscle; these are comparatively short fibres, whilst the main 
stem distributed to the caput medium and parvum and extensors of the 
foot lying in the fore-arm region is much longer, and is, therefore, not 
involved to the same extent in any strain occurring here. The correct¬ 
ness of this view is supported both by the fact that partial paralysis 
occurs accidentally after mechanical injuries, and that in such cases 
function is always retained in the extensors of the knee, of the fetlock, 
and of the foot. 
As already stated, paralysis in these groups of muscles can be detected 
during movement both by sight and feeling. Muscular atrophy occurs 
soonei oi later, and to an extent varying according to the amount of 
functional disturbance. Sometimes, though not invariably, sensation is 
lost in the skin covering the anterior and external surface of the fore arm. 
The diagnosis of radial paralysis is therefore easy. 
Differential diagnosis. The disease may be mistaken for myopathic 
lameness of the caput gioup of muscles, or for any of those conditions in 
which they partially or completely fail to act. This is particularly true 
of oblique fiactuie of the ulna the lower point of insertion of these 
muscles -and of lupture of the extensor pedis. Hertel saw all the 
extensois attached to the ulna torn away, but in such cases local 
examination at once dispels any doubt. 
