LAMENESS IN THE FORE LEG 77 



Radial Paralysis. 



Described under the titles of "Radial Paralysis" and "Bra- 

 chial Paralysis," there is to be found in veterinary literature 

 a discussion of conditions which vary in character from the 

 almost insignificant form of paresis to the incurably affected con- 

 ditions wherein the whole shoulder is completely paralyzed. 



When one considers the anatomy of the brachial nerve plexus 

 and the distribution of its various branches, the location of this 

 plexus and its proximity to the first rib, and the inevitable in- 

 jury it must suffer in fracture of this bone, together with the 

 inaccessibility of the plexus, it is not strange that a correct 

 diagnosis of the various affections of the brachial plexus and 

 the radial nerve is often impossible until several days or weeks 

 have passed. And, in some instances, diagnosis is not established 

 until an autopsy has been performed. Here, too, we fail to find 

 cause for paralysis in some rare instances. 



Anatomy. — The radial nerve is a large branch of the brachial 

 plexus and is chiefly derived from the first thoracic root of the 

 plexus and is here situated posterior to the deep brachial artery. 

 It is directed downward and backward ander the subscapularis 

 and teres major muscles, rounding the posterior part of the 

 humerus, and passing to the anterior and distal end of the 

 humerus, it finally terminates in the anterior carpal region. The 

 radial nerve supplies branches to the three heads of the triceps 

 brachii, to the common and lateral extensors of the digit and also 

 to the skin covering the forearm. 



Etiology and Occurrence.— Nothing definite is known about 

 the cause of some forms of radial paralysis. However, radial 

 paralysis is encountered following injury to the nerve occasioned 

 by its being stretched, as in cases where the triceps brachii is 

 unduly extended in restraining subjects by means of a casting 

 harness. Berns^ states that in confining horses on an old oper- 

 ating table where it was necessary to draw the affected foot for- 

 ward twenty-four to thirty-six inches in advance of its fellow. 



i"Radial Paralysis and Its Treatment by Mechanical Fixation of Knee and 

 Anltle," Geo. H. Berns, D. V. S. Proceedings of the American Veterinary 

 Medical Association, 1912, i). 219. 



