historical evolution that forms the theme of the last chapter, and consequently those which bear on the natural causes of homicide. It is necessary, therefore, to commence with animals and end with man, who is but the last link in the same chain.
Simplifying and generalizing the elementary notions that prevail on the matter of homicide, it may be said that it is the destruction of one animal by another of the same species. Homicide as a criminal fact does not consist in the act of taking life—since killing in order to live is a natural law, and hence is moral—but in killing a being of the same species. All beings of a superior species kill those of an inferior one in order to nourish themselves. The deed becomes criminal only when it is unnatural. This fact of unnaturalness defines it as a crime.
Sociology of late has planted its pioneers in the ranks of zoölogy. This was done by Lombroso in his Criminal Anthropology, and on these lines all scientists work nowadays. These scientific conclusions, which affirm the strict relationship, psychological as well as physical, existing between man and the other animals, every day demonstrates as more true. Hence the embryology of murder must be sought in the obscure depths of zoö-psychology, for it is now certain that the criminal activity of man is only the reproduction of animal criminality, developed and modified by means of intelligence. Homicide is a primitive crime like theft, and can be found in nearly all its forms and variety of motives in the animal world. As in man so in beasts there are races more prone than others to the taking of life, beings who transmit the murderous instinct. The classification of animal criminology made by Ferri can therefore be extended to man. Utilizing the studies and researches in animal psychology made up to the present, the author classifies in convenient grades a goodly number of the most accredited facts, demonstrating how homicide manifests itself in the animal kingdom. These facts are more numerous than would be generally imagined, and well adapted for precise classification. The first group, which relates to the different aspects of the struggle for life, nutrition, social supremacy, and sexual reproduction, deals with the crimes due to the natural laws of existence. The general character of this group presents a minor degree of perversion than those of premeditated ones of the second group, which includes murder determined by an instinct in the species. Animals destroy each other from sexual instinct, for love, maternal affection, for defense, for the common weal, for punishment. With respect to this last motive—punishment—among animals, which some deny, considering it a mere question of vendetta, Ferri maintains that among animals, besides this motive, there exists a more or less exact notion of chastisement. Our author admits that it is difficult to distinguish the sentiment