290 ABRAM T. KERR 



and one the brachial branch of the first thoracic nerve." Har- 

 man ('00) found the connection in 7 out of 12 dissections. Pat- 

 erson ('96) found the connection in only 11 out of 33 cases. 

 Harris ('04) states that it is "only in the postfixed types, in which 

 it might be expected" that the second thoracic nerve joins the 

 first and thus contributes to the plexus. Cunningham (77) 

 believed that the branch from the second thoracic nerve to join 

 the brachial plexus is influenced by the size of the intercosto- 

 brachial nerve. Adolphi ('98) thinks that there is no reciprocal 

 relation between the second thoracic branch to the first and the 

 intercostobrachial nerve. He considers this connection a varia- 

 tion that is associated with a more cephalic or caudal type of 

 plexus and with variations of the thorax and vertebral column. 

 Birmingham ('95) has shown how the communication between 

 the first and second thoracic nerves contributes to the intercostal 

 nerves. The intimate relation and the variability of the con- 

 nection between the first and second thoracic nerves and the 

 neighboring sympathetic ganglia has been pointed out by Har- 

 man ('00). 



From the above statement it is clear, I think, that there is 

 much difference of opinion among anatomists concerning the 

 arrangement and connections of the nerves of this region and 

 that they are not well understood and need further study. 



DIVISION OF THE PLEXUSES INTO GROUPS 



In studying the plexuses it was seen at once that they varied 

 in the number and amount of cervical spinal nerves entering 

 them at their cephalic border. 



All those plexuses in which a branch from the fourth cervical 

 nerve enters the plexus fall into one group that has been desig- 

 nated as group 1. The size of this branch varies from a minute 

 twig to a branch as large as the average suprascapular nerve. 

 The group has not been subdivided because of the difference in 

 size of the branch from the fourth nerve. There are 110 of the 

 175 satisfactory records or 62.85 per cent of the cases that fall 

 in group 1. 



