the doctrine of Free Trade so neither is it in most of the questions which arise respecting the limits of that doctrine: as for example, what amount of public control is admissible for the prevention of fraud by adulteration; how far sanitary precautions, or arrangements to protect work-people employed in dangerous occupations, should be enforced on employers. Such questions involve considerations of liberty, only in so far as leaving people to themselves is always better, caeteris paribus, than controlling them: but that they may be legitimately controlled for these ends, is in principle undeniable. On the other hand, there are questions relating to interference with trade which are essentially questions of liberty; such as the Maine Law, already touched upon; the prohibition of the importation of opium into China; the restriction of the sale of poisons;