lain of diplopia when he looks
downward.

V. _Trigeminal Nerve._--The most important surgical affection of this
nerve is "trigeminal neuralgia," which has already been described
(Volume I., p. 373). One or other of the divisions of the nerve may be
torn in fractures of the base of the skull, and there results
anaesthesia in the area supplied by it. In fractures crossing the apex
of the petrous portion of the temporal bone, the great and small
superficial petrosal nerves may be ruptured, and the soft palate and
uvula are paralysed and there is difficulty in swallowing; there are
also painful sensations in the ear. When the ophthalmic division is
implicated, the conjunctiva is rendered insensitive, and
conjunctivitis, which may be followed by ulceration of the cornea,
results from exposure to dust and other foreign bodies, which, on
account of the anaesthetic condition of the eye, are allowed to remain
and cause irritation.

VI. _Abducens Nerve._--This nerve, which supplies the lateral rectus
muscle, has the longest course within the skull of any of the cranial
nerves. In spite of this fact, it is comparatively seldom torn in
basal fractures; but it is prone to be pressed upon by tumours,
gummas, or aneurysms in the region of the base of the brain. When it
is paralysed, medial strabismus results.

VII. _Facial Nerve._--Paralysis of the facial muscles, more or less
complete, is the most characteristic symptom of lesions of this nerve.

_Paralysis of the Cerebral Type._--When the fibres of the nerve are
implicated in any part of their course between the cortical centre
and the nucleus in the lower part of the pons, the paralysis is of the
upper neurone (cerebral) type. It affects the side of the face
opposite to that of the lesion, and the defective movement is more
marked in the lower than in the upper half of the face.

This form of facial paralysis may be due to the pressure of an
intra-cranial tumour, abscess, or haemorrhage, or to degenerative
processes in the cerebral tissue, and as a rule other cranial nerves
are also affected. Its recognition is chiefly of diagnostic and
localising importance.

_Paralysis of the Peripheral Type._--When the trunk of the nerve is
implicated between the pontine nucleus and its peripheral
distribution, the paralysis is of the lower neurone (peripheral) type,
the muscles on the same side as the lesion being flaccid and
atrophied.

The majority of cases are of the so-called "rhe