Lombroso was led to formulate his doctrine of the criminal, not through the influence of the earlier workers in the same field, whose names were mentioned at the end of the last chapter, but as a natural consequence of the idea which dominated his whole mental development. This leading idea—a part of the teaching of anthropological materialism—is, on the one hand, that a man’s mode of feeling, and therewith the actual conduct of his life, are determined by his physical constitution; and, on the other hand, that this constitution must find expression in his bodily structure. He was led to the more definite formulation of this idea by chance anatomical discoveries (_vide_ _Arch. ital. delle malattie nervose_, and also _R.C. dell’ Istituto Lombardo_, 1871, v., fasc. 18)[9] in the corpses of criminals, one of which, the so-called “median occipital fossa,” had not been noticed by previous observers; this is found in most of the lower mammals, as well as in many monkeys. This first discovery of the kind has since been supplemented by a large number of others: in part such as were in the first instance most carefully observed by Lombroso and his pupils; in part those described by other anthropologists as “theromorphs”; in part those enumerated by Darwinian naturalists as “atavisms”—that is, characters regarded and described as vestiges inherited from the prehuman ancestors of our species. If we compare the writings of those zoologists and anatomists who treat of these questions, with those of Lombroso and his followers, we cannot fail to notice the complete independence of the Italians, and at the same time their more comprehensive grasp, and their better knowledge of prehistoric data. The anthropologists of the Italian school usually went to work in the following way. If in examining the body of a criminal they came across a theromorph in any organ, or observed any other unusual structure, they propounded certain questions regarding the peculiarity, viz.: 1. Is this peculiarity present in any of the authentic remains of prehistoric man, and, if so, how often is it met with in these, as compared with the frequency of its presence in the bodies of criminals? 2. Is it met with in the lower races of man, and, if so, how often? (The answer to this question is obtained by examining the skulls, etc., of these lower races, to be found in European museums.) 3. Is it found in the higher apes, and, if so, is it an occasional or a constant feature? 4. Is it found in other species of the group of primates? 5. Is it found in animals lower than these in the scale of classification? 6. Is it found in human beings presenting congenital morbid anomalies; more especially is it found in epileptics and in idiots?