robbery and burglary are generally counted as crimes of violence, but they should be properly classed under property crimes. every motive that leads to getting property in illegal ways applies to these crimes. there is added to the regular causes of property crimes the element of danger and adventure which makes a strong appeal to boys and men. i am inclined to think that few mature men have committed one of these crimes, unless they began criminal careers as boys. such crimes especially appeal to the activity and love of adventure which inhere in every boy. they are committed for the most part by youths who have had almost no chance to get the needed sport and physical experience incident to boyhood. the foot-ball, base-ball, polo or golf player very seldom becomes a robber or a burglar. almost no rich man or rich man's son becomes a robber or a burglar. those who fall under this lure are mainly the denizens of the streets, the railroad yards, the vacant lots, the casual workers who are stimulated by a variety of conditions to get property unlawfully. added to this are almost invariably a defective heredity, vicious environment, little education, and a total want of direction in the building up of habits and inhibitions.

the robber or burglar who kills in the commission of crime is more dangerous and harder to cure than the one who kills from passion or malice. there is always the element of an occupation, for getting property, and generally a love of adventure that is difficult to overcome, except by a substantial change of social relations which makes acquiring property easier for the class from which all these criminals develop. the murder that comes from passion and feeling implies situations and circumstances that are rarely strong enough to overcome the restrictions against killing.