The Lower Limbs. Of a number of criminals examined, 16% showed an unusual development of the third trochanter, a protuberance on the head of the femur where it articulates with the pelvis. This distinctly atavistic character is connected with the position of the hind-limb in quadrupeds.
The Feet. Spaces between the toes like the interdigital spaces of the hand are very common, and in conjunction with the greater mobility of the toes and greater length of the big-toe, produce the prehensile foot, of the quadrumana, which is used for grasping. The foot is often flat, as in negroes. In the feet, as in the hands, there is frequently a tendency to greater strength or dexterity on the left side, contrary to what happens in normal persons, and this tendency is manifested in many cases where there is no trace of functional and motorial left-handedness.
The Cerebrum and the Cerebellum. The chief and most common anomaly is the prevalence of macroscopic anomalies in the left hemisphere, which are correlated to the sensory and functional left-handedness common to criminals and acquired through illness. The most notable anomaly of the cerebellum is the hypertrophy of the vermis, which represents the middle lobe found in the lower mammals. Anomalies in the cerebral convolutions consist principally of anastomotic folds, the doubling of the fissure of Rolando, the frequent existence of a fourth 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.