The criminal skull does not exhibit any marked characteristics of size and shape. Generally speaking, it tends to be larger or smaller than the average skull common to the region or country from which the criminal hails. It varies between 1200 and 1600 c.c.; i.e., between 73 and 100 cubic inches, the normal average being 92. This applies also to the cephalic index; that is, the ratio of the maximum width to the maximum length of the skull[1] multiplied by 100, which serves to give a concrete idea of the form of the skull, because the higher the index, the nearer the skull approaches a spherical form, and the lower the index, the more elongated it becomes. The skulls of criminals have no characteristic cephalic index, but tend to an exaggeration of the ethnical type prevalent in their native countries. In regions where dolichocephaly (index less than 80) abounds, the skulls of criminals show a very low index; if, on the contrary, they are natives of districts where brachycephaly (index 80 or more) prevails, they exhibit a very high index.
SKULL FORMATION
| Fig. 2 | Fig. 3 |
In 15.5% we find trochocephalous or abnormally round heads (index 91). A very high percentage (nearly double that of normal individuals) have submicrocephalous or small skulls. In other cases the skull is excessively large (macrocephaly) or abnormally small and ill-shaped with a narrow, receding forehead (microcephaly, 0.2%). More rarely the skull is of normal size, but shaped like the keel of a boat (scaphocephaly, 0.1% and subscaphocephaly 6%). (See [Fig. 2].) Sometimes the anomalies are still more serious and we find wholly asymmetrical skulls with protuberances on either side (plagiocephaly 10.9%, see [Fig. 3]), or terminating in a peak on the bregma or anterior fontanel (acrocephaly, see [Fig. 4]), or depressed in the middle (cymbocephaly, sphenocephaly). At times, there are crests or grooves along the sutures (11.9%) or the cranial bones are abnormally thick, a characteristic of savage peoples (36.6%) or abnormally thin (8.10%). Other anomalies of importance are the presence of Wormian bones in the sutures of the skull (21.22%), the bone of the Incas already alluded to (4%), and above all, the median occipital fossa. Of great importance also are the prominent frontal sinuses found in 25% (double that of normal individuals), the semicircular line of the temples, which is sometimes so exaggerated that it forms a ridge and is correlated to an excessive development of the temporal muscles, a common characteristic of primates and carnivores. Sometimes the forehead is receding, as in apes (19%), or low and narrow (10%).
The Face. In striking contrast to the narrow forehead and low vault of the skull, the face of the criminal, like those of most animals, is of disproportionate size, a phenomenon intimately connected with the greater development of the senses as compared with that of the nervous centres. Prognathism, the projection of the lower portion of the face beyond the forehead, is found in 45.7% of criminals. Progeneismus, the projection of the lower teeth and jaw beyond the upper, is found in 38%, whereas among normal persons the proportion is barely 28%. As a natural consequence of this predominance of the lower portion of the face, the orbital arches and zygomæ show a corresponding development (35%) and the size of the jaws is naturally increased, the mean diameter being 103.9 mm. (4.09 inches) as against 93 mm. (3.66 inches) in normal persons. Among criminals 29% have voluminous jaws.
The excessive dimensions of the jaws and cheek-bones admit of other explanations besides the atavistic one of a greater development of the masticatory system. They may have been influenced by the habit of certain gestures, the setting of the teeth or tension of the muscles of the mouth, which accompany violent muscular efforts and are natural to men who form energetic or violent resolves and meditate plans of revenge.
Asymmetry is a common characteristic of the criminal physiognomy. The eyes and ears are frequently situated at different levels and are of unequal size, the nose slants towards one side, etc. This asymmetry, as we shall see later, is connected with marked irregularities in the senses and functions.
The Eye. This window, through which the mind opens to the outer world, is naturally the centre of many anomalies of a psychic character, hard expression, shifty glance, which are difficult to describe but are, nevertheless, apparent to all observers (see [Fig. 4]). Side by side with peculiarities of expression, we find many physical anomalies—ptosis, a drooping of the upper eyelid, which gives the eye a half-closed appearance and is frequently unilateral; and strabismus, a want of parallelism between the visual axes, which is insignificant if it arises from errors of refraction, but is very serious if it betokens progressive or congenital diseases of the brain or its membranous coverings. Other anomalies are asymmetry of the iris, which frequently differs in colour from its fellow; oblique eyelids, a Mongolian characteristic, with the edge of the upper eyelid folding inward or a prolongation of the internal fold of the eyelid, which Metchnikoff regards as a persistence of embryonic characters.
The Ear. The external ear is often of large size; occasionally also it is smaller than the ears of normal individuals. Twenty-eight per cent. of criminals have handle-shaped ears standing out from the face as in the chimpanzee: in other cases they are placed at different levels. Frequently too, we find misshapen, flattened ears, devoid of helix, tragus, and anti-tragus, and with a protuberance on the upper part of the posterior margin (Darwin's tubercle), a relic of the pointed ear characteristic of apes. Anomalies are also found in the lobe, which in some cases adheres too closely to the face, or is of huge size as in the ancient Egyptians; in other cases, the lobe is entirely absent, or is atrophied till the ear assumes a form like that common to apes.