ys able to localise the sensation exactly: inability to
do so signifies disease of the brain or some kind of anomaly.

_Sensibility to Metals_ is tested by placing discs of different metals,
copper, zinc, lead, and gold, or the poles of a magnet, on the frontal
and occipital parts of the patient's head. Sometimes he feels pricking
or heat, giddiness, somnolence, or a sense of bodily well-being. In
general, criminals show great sensibility to metals; in hysterical
persons this sensibility reaches an extraordinary degree of acuteness.
By applying a magnet to the nape of the neck, the sensations of such
individuals become polarised, that is, what appeared white to them
before becomes black; bitter, what was formerly sweet, or vice versa.
This is an excellent way of distinguishing between bona-fide cases of
hysteria and sham ones. My father once detected simulation in a
_soi-disant_ hysterical patient by means of a piece of wood shaped and
coloured to represent a magnet. On application of either magnet, the
real or sham one, the patient's sensations were identical, whereas
hysterical persons experience very diverse sensations and are able to
distinguish very sharply between the contact, not only of wood and
metal, but of the different kinds of metal, and are particularly
sensitive to the magnet.

=FIG. 35
ALGOMETER
(see page 246)=

=FIG. 36
CAMPIMETER OF LANDOLT
(Modified)
(see page 249)=

_Sight--Acuteness of Vision--Chromatic Sensibility--Field of Vision._
Visual acuteness is tested by holding letters of a specified size at a
certain distance. Sight is generally more acute in criminals than in
normal persons; not so, chromatic sensibility, which is tested by giving
the patient a number of skeins of different coloured silks, and
requesting him to arrange them in series. Persons afflicted with
dyschromatopsia confuse the different colours and the different shades
of the same colour. Colour-blind people confuse black and red.

Especially important is the examination of the field of vision, as the
seat of one of the most serious anomalies discovered by the Modern
School, the presence of peripheral scotoma, frequently found in
epileptics and born criminals. To test this anomaly, use should be made
of Landolt's apparatus (Fig. 36). This consists of a semicircular band,
which can revolve around a column. The patient rests his chin on a
support placed in front of the semicircle in such a manner that the