to reach; while those that develop in more accessible regions are for
the most part infiltrating growths of a gliomatous or sarcomatous
nature, and are therefore irremovable.

_Clinical Features._--The presence of a tumour in the brain inevitably
results sooner or later in an increase in the intra-cranial tension,
and to this the symptoms are chiefly due.

The earliest and most prominent of the _general symptoms_ are severe
paroxysmal headache, optic neuritis, with choked disc and limitation
of the field for blue, amounting sometimes to blue-blindness
(Cushing). The relative degree of neuritis in the two eyes is a
reliable guide to the side on which the tumour is situated (Horsley).
The symptoms are seldom absent, and are common to all forms of tumour,
wherever situated. Vomiting, which is without relation to the taking
of food and is usually unattended by nausea, is a characteristic
symptom when present, but it is wanting in two-thirds of the cases
(Cushing). Vertigo, general convulsions, and signs of mental
deterioration are also present in a considerable proportion of cases.

In addition, certain _localising symptoms_ may be present. When, for
example, the tumour is situated in the _cortex of the Rolandic area_,
attacks of Jacksonian epilepsy, preceded by an aura, which is usually
referable to the centre primarily implicated, are common. The group of
muscles first involved, and the order in which other groups become
affected, are important localising factors. As the tumour increases in
size, these irritative phenomena are replaced by localised paralyses.
The tactile and muscular sensations are also disturbed, and motor and
sensory aphasia may be present. In some cases localised tenderness on
percussing the skull may be of assistance in indicating the site of
the tumour.

When the tumour is _sub-cortical_, that is, in the centrum ovale,
there are no Jacksonian spasms, the motor paralysis is more
widespread, and sensation also is lost on the opposite side of the
body. There is no special tenderness on percussion. It is not always
possible, however, to distinguish between cortical and sub-cortical
tumours, and in many cases both areas are invaded.

Tumours situated in the region of _the internal capsule_, and _in the
deeper parts of the brain_, are not attended with Jacksonian spasms,
paralysis develops more rapidly than in cortical and sub-cortical
tumours, and there is complete loss of sensation on the opposite