h nerve_ was occasionally damaged in wounds of the floor of
the mouth. I saw no case of permanent paralysis.

_Injury to the systemic nerves._ _Cervical plexus._--Evidence of injury
to the superficial branches of the cervical plexus was not rare; thus I
saw cases of small occipital anaesthesia, and great occipital neuralgia,
but none of motor paralysis from injury to the deeper muscular branches.
I take it that the smallness of the branches, and the multiple supply
possessed by many of the muscles of the neck, would both take part in
rendering certain evidence of the injury of an individual motor nerve
rare.

_Brachial plexus._--Injury to this plexus in the neck was common; the
main peculiarity observed was the partial nature of the damage
inflicted.

Thus injury to a single nerve, or to a complex of two or more, was far
more common than one implicating the whole plexus. Again, while complete
paralysis might affect one set of nerves, another might simply exhibit
signs of irritation in the form of hyperaesthesia or pain.

The wounds producing these injuries varied much in direction; thus some
crossed the neck transversely, some were obliquely transverse, while
others took a more or less vertical course.

These same remarks hold good in the case of the nerves of the arm. In
the upper half, especially, complex injury was not rare, while in the
lower third affection of individual nerves was more common. Another
important difference must be mentioned in regard to the upper and lower
segments of the course of the brachial nerves; they are not only more
widely distributed below, but also more fixed in position, a fact
antagonistic to the escape of the nerve by displacement and liable to
expose it to more severe contusion.

The latter point holds good in the forearm also; here, individual
injuries often occurred.

While at work in the Field hospital alone I gained the impression that
the musculo-spiral nerve would not retain the unenviable character of
being the most vulnerable nerve of the upper extremity, since the
chances of each individual nerve seemed about equal, putting the
question of the long course of the musculo-spiral nerve against the
humerus out of question. This expectation was, however, not confirmed,
since the musculo-spiral itself, if not primarily affected, was so often
the seat of secondary mischief in fractures of the humerus. The
posterior interosseous branch seemed to exhibit a similar vulnerabili