BRACHIAL PLEXUS OF NERVlIS IN MAN 349 



the other comes from a small dorsal division of the caudal trunk 

 that joins the posterior fasciculus. Both anastomose with the 

 intercostobrachial. In one case both branches arise from the 

 first thoracic nerve and one of them anastomoses with the inter- 

 costobrachial. There is one instance where there are 3 branches 

 that were classified as medial brachial cutaneous nerves; these 

 all arise from the medial fasciculus of the plexus from a stem from 

 which the medial antibrachial cutaneous also arises. One or two of 

 them might possibly be classified as branches of this latter nerve. 



The medial brachial cutaneous nerve arises by itself from one 

 of the main branches of the brachial plexus in 103 of the 137 

 plexuses where there was a single nerve. 



In 20 instances the single medial brachial cutaneous arises 

 from a stem common to it and the medial antibrachial cutaneous; 

 in 5 from a stem common to it and the medial anterior thoracic ; 

 and in 8 from a stem common to it and both of the above nerves. 

 In the 29 cases where there are two or more nerves, there are 59 

 nerves recorded and 42 of these arise separately; 10 with the 

 medial antibrachial cutaneous; 6 with the medial anterior tho- 

 racic ; and one with both of these nerves. It will be seen then that 

 the medial brachial cutaneous arises from the plexus as an in- 

 dependent branch in 73.97 per cent of the cases. 



The records show that the medial brachial cutaneous nerve 

 anastomoses with the intercostobrachial in 101 instances or in 

 60.84 per cent of the cases. There is no doubt that there were 

 many other plexuses in which such a connection existed but it 

 was broken before the record could be verified. 



The medial brachial cutaneous nerve arises from the caudal 

 trunk of the brachial plexus or one of the divisions of this in 157 

 of the 166 plexuses. It therefore may receive fibers from the 

 eighth cervical and first thoracic in all of these. In addition, 

 there is one case where it arises from these nerves by separate 

 roots. The eighth cervical and first thoracic nerves may send 

 fibers to it in 95.18 per cent of the cases. In one of the type 

 A plexuses it arises from the caudal trunk distal to the point 

 where the branch from the seventh cervical joins this trunk so 

 that in this case the seventh cervical cannot be excluded. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 23, NO. 2 



