The orbital capacity has been noted by Lombroso and others to be frequently larger than normal (as among birds of prey and some savages), especially among thieves. There is marked exaggeration of the orbital arches and frontal sinuses which may be related, at all events in the cases of individuals living in the country, with energy of the respiratory system.
Receding foreheads, very commonly observed among criminals, have always been regarded as evidence of low mental and moral organisation, not without reason, though it must be remembered, as Ten-Kate and Benedikt point out, that the breadth, vaulting, and general size of the head must be taken into consideration. Many men of marked intellectual power have had receding foreheads.
Tenchini has pointed out (and the observation has since been confirmed) that the frontal crest is often stronger and more prominent in criminals. In normal skulls he found it 3-4 millimetres in length; in criminals frequently 5-6 mm. It is also larger in the insane and lower races, and relatively larger in orang-outangs. It may signify precocious union of the two parts of the frontal bone with consequent arrest of brain development.
The presence of a median occipital fossa has been specially noted by Lombroso, sometimes in connection with hypertrophy of the vermis of the cerebellum, as among the lower apes, in the human foetus between the third and fourth months, and in some lower races.
Lack of cranial symmetry is one of the most marked features of the criminal skull, although it has not often at present been subjected to exact measurement.[18] It must be remembered that every skull, criminal or non-criminal, is deficient in strict symmetry (and, indeed, every part of the body likewise), and that statistics therefore are here of little value; it is simply a question of the amount of asymmetry; and two observers going over the same series of skulls would almost certainly come to different conclusions. They would probably, however, both find the proportion of asymmetrical heads greater in the criminal than in the ordinary series.
All these cranial abnormalities are found occasionally in ordinary persons; very rarely are they found combined in normal persons to the extent that they are found among instinctive criminals. Thus Lombroso, when he examined the skull of Gasparone, a famous brigand of the beginning of the century, whose name still lives in legends and poems, found microcephaly of the frontal region, a wormian bone, eurigmatism, increase in the orbital capacity, oxycephaly, and extreme dolichocephaly. Mingazzini found that out of thirty criminals eight presented brains and skulls of a weight and capacity only found in submicrocephalic subjects; that several of these showed, either in brain or skull, or both, the union of several anomalies; and that in the skulls of other six the abnormal appearances were so manifold as to present an aspect which might be called "completely teratologic."[19] Most of these anomalies are found much more frequently in the male than in the female skull. If, however, the criminal woman is compared with the normal woman, she is found to approach more closely to the normal man than the latter does; while the corresponding character (feminility) is not found so often in the criminal as in the normal man, except among pæderasts and some thieves. It may also be mentioned that nearly all these anomalies are much more rarely found in the insane.