130 
of the human subjects which he examined (1). ELLIOT SMITH (3) 
and BIRMINGHAM (2) have also deseribed the same communication. 
After emerging from the intervertebral foramen the first dorsal 
nerve divides into an upper portion (x) which joins the brachial 
plexus in front of the neck of the first rib, and a lower portion (6) 
which supplies the first intercostal space (see Fig. 1). CUNNINGHAM 
states that the communication from the second dorsal nerve, though 
variable in size, is usually small, 
and may join either or both por- 
CV. : \ 
tions of the first dorsal nerve (1). 
ELLIOT SMITH has shown that 
the communication to the lower 
CVI. : ; 
portion of the first dorsal nerve 
assists in the supply of the first 
intercostal space. It may supply 
Cvll. the space directly and in such 
cases it does not communicate 
with the first nerve (3). The 
FA au 
mage 
work of the last-mentioned writer 
makes clear the function of the 
communication when it joins the 
lower portion only of the first 
we ß DI. ‘ The. fanctiondl Seemed 
nerve. ve functional signific 
ance of the communication to the 
DI. upper portion of the first nerve, 
I is however, still uncertain. As 
Fig. 1. Diagram of the right Brachial ELLIOT SMITH remarks, it may 
Plexus to show the communication passing u Fi 
from the 2nd dorsal nerve to join the be so small as to be quite inade- 
brachial («) and intercostal (#) portions of quate to carry to the brachial 
ie wareh dorsal naive, plexus the fibres which ultimately 
pass into the lesser internal cuta- 
neous, (N. cutaneus brachii medialis), and intercosto-humeral nerves 
(Nn. intercosto-brachiales). This writer then makes the very important 
suggestion that an intracentral passage of fibres from the nucleus of 
the second dorsal nerve takes place, some of the fibres from the second 
dorsal nucleus in this manner passing out along the first nerve (3). 
In the preparation of certain dissections for another investigation (22) 
the variation noted in the size of this communication when it was 
present and the close relation which it sometimes presents to the 
