all cases, in short, where the object of the interference is to make it impossible or difficult to obtain a particular commodity.

These interferences are objectionable, not as infringements on the liberty of the producer or seller, but on that of the buyer.

One of these examples, that of the sale of poisons, opens a new question; the proper limits of what may be called the functions of police; how far liberty may legitimately be invaded for the prevention of crime, or of accident. It is one of the undisputed functions of government to take precautions against crime before it has been committed, as well as to detect and punish it afterwards. The preventive function of government, however, is far more liable to be abused, to the prejudice of liberty, than the punitory function; for there