th frontal convolution, the
imperfect development of the precuneus (as in many types of apes), etc.
Anomalies of a purely pathological character are still more common.
These are: adhesions of the meninges, thickening of the pia mater,
congestion of the meninges, partial atrophy, centres of softening,
seaming of the optic thalami, atrophy of the corpus callosum, etc.

Of great importance, too, are the histological anomalies discovered by
Roncoroni in the brains of criminals and epileptics. In normal
individuals the layers of the frontal region are disposed in the
following manner:

1. Molecular layer. 2. Superficial layer of small cells. 3. Layer of
small pyramidal cells. 4. Deep layer of small nerve cells. 5. Layer of
polymorphous cells (see Fig. 6).

In certain animals, the dog, ape, rabbit, ox, and domestic fowl, the
superficial layer is frequently non-existent and the deep one is found
only to some extent in the ape.

In born criminals and epileptics there is a prevalence of large,
pyramidal, and polymorphous cells, whereas in normal individuals small,
triangular, and star-shaped cells predominate. Also the transition from
the small superficial to the large pyramidal cells is not so regular,
and the number of nervous cells is noticeably below the average.
Whereas, moreover, in the normally constituted brain, nervous cells are
very scarce or entirely absent in the white substance, in the case of
born criminals and epileptics they abound in this part of the brain.

The abnormal morphological arrangement described by Roncoroni is
probably the anatomical expression of hereditary alterations, and
reveals disorders in nervous development which lead to moral insanity
or epilepsy according to the gravity of the morbid conditions which give
rise to them.

=FIG. 6

_a_) Cortical strata of the circumvolutions of the parietal lobes of a
normal person.

_b_) Cortical strata of the circumvolutions of the parietal lobes of a
criminal epileptic.

1. Molecular stratum. 2. External granular stratum. 3. Stratum of the
small pyramidal cells. 4. Stratum of the large pyramidal cells. 5. Deep
stratum of the small nervous cells or the deep granular stratum. 6.
Stratum of polymorphic cells. S.B. White matter.=

These anomalies in the limbs, trunk, skull and, above all, in the face,
when numerous and marked, constitute what is known to criminal
anthropologists as the criminal type, in exactly the same way