et ae EERON 
3 
a 
1884. | of the Flexuses in the Human Subject. 383 
have some fixed method of counting nerves, especially those 
which compose plexuses, with reference to their distribution in 
cervical, dorsal and other sets. If we agree to know and name 
any spinal nerve dy the vertebra above which it issues, we can 
hardly go astray. 
The principal points touching the plexuses of the human sub- 
ject may be noted in comparing the old with the new style. 
1. The cervical plexus is not affected (first four cervical 
nerves). 
2. The brachial plexus falls between the cervical and dorsal 
sets of nerves in either case, but there is a distinction in favor of 
the new numeration. The plexus is said to be formed by the 
last four cervical (5th—-8th) and first (1st) dorsal nerves ; and it is 
said that three of the cervical (5th-7th) unite to form the upper 
cord, while the last (8th) cervical and first (rst) dorsal unite to 
form the lower cord. I should say that the brachial plexus is 
formed by the last three (sth-7th) cervicals and first two ( rst-2d) 
dorsals, the former uniting in one cord, the latter in another. 
Thus the remarkable partition of the brachial plexus into two 
cords, which extend to the axilla, coincides with its derivation 
from the two sets of nerves; and further details, such as the 
union of the two dorsals as soon as they leave their respective 
foramina, show that the division of the two sets of nerves here 
made is the natural one. 
3. The so-called last (12th) dorsal or intercostal nerve (that 
‘ssuing between the last dorsal and first lumbar vertebra) is gen- 
erally noted in the text-books for various peculiarities which 
relate it to the lumbar series, besides its actual connection with 
the latter, This nerve is really first (1st) lumbar. The lumbar 
xus IS variously described as consisting of the last dorsal (12th) 
and four (Ist-4th) or five lumbar nerves (1st-5th), according to 
Whether or not its sacral connection is taken into account. I 
eo Say simply that the lumbar plexus is formed by the 
umbar nerves proper (1st-sth), with communicating loop to 
ell Sacral: plexus, Matters are here greatly simplified by the 
numeration, It is well to remember that a% contiguous plex- 
oes a communicating loop, both above and below; thus 
the Io oS between the cervical and brachial, and one between 
mbar and sacral; but such loops separate plexuses as well 
. 
