324 ABRAM T. KERR 



head of the median (fig. 3). In the 8 in which it passes to the 

 medial fasciculus, the ulnar alone, or both ulnar and median 

 nerves may be supplied by it. The fibers which pass to the 

 medial head of the median are usually collected into a single 

 fasciculus (figs. 1, 3, 8) but in a few cases they are divided into 

 2 or more small branches (fig. 14). 



In its course to the ulnar nerve the lateral head of the ulnar 

 in some cases passes dorsal to the medial head of the median 

 (fig. 1), in a few it passes ventral to the medial head of the 

 median, but in the most usual arrangement, it pierces the medial 

 head of the median (figs. 2, 3 and 8). 



In my series the lateral head of the ulnar arises from the lateral 

 fasciculus of the plexus in 40 cases (figs. 1 and 3), in 3 of these it 

 passes to the medial fasciculus of the plexus close to its division 

 into the ulnar nerve and medial head of the median nerve (fig. 11), 

 in 13 to the ulnar nerve only (fig. 13), and in 24 to the medial 

 head of the median nerve as well as to the ulnar (figs. 1 and 3). 

 In 2 of these instances the lateral head of the ulnar gives also 

 a branch to the lateral head of the median (fig. 24) . 



The lateral head of the ulnar nerve arises from the seventh 

 cervical nerve in 13 cases, in 2 of these passing to the medial 

 fasciculus of the plexus, in 3 to the ulnar nerve only and in 8 to 

 the medial head of the median nerve as well as to the ulnar nerve 

 (fig. 10). In 4 of these the lateral head of the median nerve is 

 formed in the usual way but in the other 4 it is irregular as de- 

 scribed in connection with the median. In 2 of these the seventh 

 cervical forms the lateral head of the median nerve (fig. 17), 

 so the lateral head of the ulnar in these instances arises from the 

 lateral head of the median. 



In 22 cases the lateral head of the ulnar arises from the lateral 

 head of the median nerve, in 21 of these it passes to the ulnar 

 only (fig. 2), in one case to both the ulnar and the medial head of 

 the median nerve (fig. 8) . 



In the series reported by Walsh the lateral head of the ulnar 

 arose proximal to the middle of the lateral fasciculus of the 

 plexus in 15G plexuses, in the rest more distally, in 30 arising from 

 the lateral head of the median nerve. 



