316 ABRAM T. KERR 



lateral fasciculus (fig. 6). The lateral fasciculus then receives 

 fibers from nerves caudal to the seventh. The medial fasciculus 

 is formed from the eighth cervical and first thoracic nerve. There 

 are 4 cases of this kind, or 2.28 per cent of the 175 plexuses. In 

 3 of the 4 cases, the extra branch to the lateral fasciculus comes 

 from the eighth nerve only (fig. 27). In the exceptional in- 

 stances it arises from the caudal trunk. In this case the branch 

 joins the seventh cervical before it divides into dorsal and ventral 

 branches. In another case the branch joins the ventral branch of 

 the seventh cervical. In the other two cases, the branch goes 

 to the lateral fasciculus directly. In two cases the branch also 

 sends an additional offshoot to the dorsal fasciculus. In both 

 cases where the branch to the lateral fasciculus sends a branch 

 to the dorsal fasciculus there is also another separate branch 

 from the caudal trunk to the dorsal fasciculus. 



The subgroups of group 2 I have designated types D and E. 

 They receive no fibers from the fourth cervical nerve. 



TijpeD 



In tj^pe D there is a branch from the seventh cervical nerve to 

 the medial fasciculus of the plexus (fig. 7). The medial fascic- 

 ulus is then formed of fibers from the seventh and eighth cervical 

 and first thoracic nerves and the lateral fasciculus from the fifth, 

 sixth and seventh cervical. This type is exactly like type A 

 except for the absence of the branch from the fourth cervical 

 nerve. There is only one case of this type or 0.57 per cent. 



Type E 



In type E the lateral fasciculus is formed of fibers from the 

 fifth, sixth and seventh cervical nerves and the medial fasciculus 

 of branches from the eighth cervical and first thoracic nerves 

 (Fig. 2). The plexuses of this type are exactly like the plexuses 

 of type B except that the branch from the fourth cervical nerve 

 does not join them. There are 51 plexuses of this type or 29.14 

 per cent of the 175 plexuses. 



Group 3 plexuses were divided into tj^pes F and G. The 

 whole of the fifth cervical does not contribute to this type. 



