inferior angle
of the parietal bone, and in the line of the sagittal suture. Very
rarely they occur at the base of the skull and project into the
pharynx, the mouth, or the nose, where they are liable to be mistaken
for polypi. Cephaloceles vary greatly in size, some being so small as
almost to escape detection, while others are larger than a child's
head. In many cases the condition is incompatible with life.

Several varieties are recognised. They are known as (1)
_meningocele_, which consists of a protrusion of a cul-de-sac of the
arachno-pial membrane, containing cerebro-spinal fluid; (2)
_encephalocele_, in which a portion of the brain is protruded in
addition to the membranes; and (3) _hydrencephalocele_, in which the
protruded portion of brain includes a part of one of the ventricles.

_Clinical Features._--The _meningocele_ is commonest in the occipital
region, where it escapes through a cleft in the bone between the
foramen magnum and the occipital protuberance (Fig. 197). It forms a
tense, smooth, translucent globular swelling, which may be sessile or
pedunculated, and is usually covered by thin, smooth skin in which the
vessels are dilated and naevoid. The tumour does not pulsate, but
increases in size and tension when the child cries or coughs. It may
be diminished in size or even made to disappear by pressure, and so
permit of the opening in the bone being felt. This manipulation,
however, may be followed by slowing of the pulse, vomiting, loss of
consciousness, or convulsions.

[Illustration: FIG. 197.--Occipital Meningocele.

(From a photograph lent by Sir George T. Beatson.)]

Small meningoceles may remain stationary for a long time, or may even
undergo spontaneous cure. Those of larger size usually progress till
they eventually burst, and death results from the escape of the
cerebro-spinal fluid or from meningitis. Infection may also occur
from eczema or from excoriation of the overlying skin.

_Encephaloceles_ are much commoner than meningoceles, and usually
occur in the frontal region, where they form broad-based, elastic, and
pulsatile tumours, which vary greatly in size.

The _hydrencephalocele_ is usually met with in the occipital region,
and is generally so large and associated with such great cerebral
deformity as to be inconsistent with life. It does not as a rule
pulsate (Fig. 198).

[Illustration: FIG. 198.--Frontal Hydrencephalocele.

(From a photograph lent by Sir George T. Beats