In passing from the tariff, or duties on imports, to the internal or excise taxes imposed by the Federal Government, there is evidently a distinct change in purpose. However subject to abuse the tax on distilled spirits has proved, and however frequently its agency has been invoked to exaggerate the profits of interested parties, there has never been an open and avowed intention of turning it to private gain. The policy that has become almost inseparable from the customs tariff, and is by most people regarded as inherent in all customs legislation, has not been transferred to the internal revenue taxes save in one or two instances of recent application and secondary importance. The danger of permitting taxation to be employed by either State or Federal Government for a purpose other than that of raising necessary revenue has been dwelt upon. When a police power is exercised in conjunction with a tax framed for revenue, and is regarded as the more important function to be performed, the policy requires careful examination. If revenue is the real object, the method of imposing the tax and the determination of the rate which will give the highest return with the least interference in the production, distribution, and export of the commodity taxed remains to be defined. If restriction in manufacture, sale, or consumption is intended, the question is no longer one of taxation proper, but of police regulation. The Federal taxes on oleomargarine, filled cheese, and mixed flour are of the nature of police inspection, and the tax on the circulation of State banks, amounting, as it has, to prohibition, is a still more extreme exercise of the same power. The imposition and collection of these duties have a penal quality, an intention to restrict or prohibit the production or sale or use of some article. They are not properly taxes; they are not a proper application of tax principles, but have originated, in private interest, or in the deliberate intention to constitute a monopoly, State or other.