The study of the brains of criminals subsequently moved in two directions: whereas Benedikt, the talented and original Viennese investigator, and after him a number of Italian investigators, studied the fissures and sulci by which the surface of the human brain is divided into convolutions in such a remarkable manner; during the years 1894 to 1900, the more limited circle of Lombroso and his immediate pupils was engaged in the study of atavistic anomalies, and of those more delicate peculiarities of the intimate structure of the brain which can be demonstrated only with the aid of the microscope. Moreover, the study of the convolutions in the brains of criminals has led to the discovery of a number of characters which may be regarded as atavistic. Most of these are primatoid varieties—that is to say, either they are manifestations of an abnormally slight development of those peculiarities of the convolutions by which the members of the human species are distinguished from the other primates, or else they are characters which are not normally found in human beings at all, although they exist normally in other primates. In a tabular comparison of the differences between the human and the simian brain, we observe that these differences are precisely those in respect of which the deviations of the criminal brain from the normal human type of brain are also manifested. In other words, the human brain is an advanced type of the brain of the primates in general, but in the brain of the criminal the resemblances to the simian type are much more strongly marked. It is, indeed, quite impossible to explain the abnormal moral and social behaviour of the criminal with reference merely to the abnormal configuration of the criminal’s cerebral convolutions. Perhaps the human contemporaries of the cave-bear in Europe possessed a brain, and, _mutatis mutandis_, exhibited in many respects a mode of life analogous to that of the modern Sardinian bandit, of the London street arab, the _voyou_ of Montmartre, or the fugitive from the Siberian mines. But in the Stone Age there existed no economically developed society upon which our palæolithic progenitor could become parasitic. We know almost nothing about post-glacial man. It may be possible at some future date, from a chart of the surface of the brain, to deduce the social characteristics of the race; but, although at present this deduction remains beyond our powers—and perhaps will never become easy—the primatoid character of the cerebral convolutions of the criminal possesses, none the less, a profound anthropological significance. No ethnologist is able from an examination of the convolutions of a Greenlander’s brain to deduce the national characteristics of the race to which the possessor of the brain belonged; but, nevertheless, when we see a brain with certain characteristics we are able to declare it to be the brain of a Greenlander.[13]