An examination of the senses and sensibility of criminals gives the following results:
_General Sensibility._ Tested simply by touching with the finger, a certain degree of obtuseness is noted. By using an apparatus invented by Du Bois-Reymond and adopted by my father, the degree of sensibility obtained was 49.6 mm. in criminals as against 64.2 mm. in normal individuals. Criminals are more sensitive on the left side, contrary to normal persons, in whom greater sensibility prevails on the right.
_Sensibility to Pain._ Compared with ordinary individuals, the criminal shows greater insensibility to pain as well as to touch. This obtuseness sometimes reaches complete analgesia or total absence of feeling (16%), a phenomenon never encountered in normal persons. The mean degree of dolorific sensibility in criminals is 34.1 mm. whereas it is rarely lower than 40 mm. in normal individuals. Here again the left-handedness of criminals becomes apparent, 39% showing greater sensibility on the left.
_Tactile Sensibility._ The distance at which two points applied to the finger-tips are felt separately is more than 4 mm. in 30% of criminals, a degree of obtuseness only found in 4% of normal individuals. Criminals exhibit greater tactile sensibility on the left. Tactile obtuseness varies with the class of crime practised by the individual. While in burglars, swindlers, and assaulters, it is double that of normal persons, in murderers, violators, and incendiaries it is often four or five times as great.
_Sensibility to the Magnet_, which scarcely exists in normal persons, is common to a marked degree in criminals (48%).
_Meteoric Sensibility._ This is far more apparent in criminals and the insane than in normal individuals. With variations of temperature and atmospheric pressure, both criminals and lunatics become agitated and manifest changes of disposition and sensations of various kinds, which are rarely experienced by normal persons.
_Sight_ is generally acute, perhaps more so than in ordinary individuals, and in this the criminal resembles the savage. Chromatic sensibility, on the contrary, is decidedly defective, the percentage of colour-blindness being twice that of normal persons. The field of vision is frequently limited by the white and exhibits much stranger anomalies, a special irregularity of outline with deep peripheral scotoma, which we shall see is a special characteristic of the epileptic.