One of the classic definitions of the Police Power is that of Chief Justice Shaw, given in his opinion in Commonwealth v. Alger.4 He says: "We think it is a settled principle, growing out of the nature of well-ordered civil society, that every owner of property, however absolute and unqualified may be his title, holds it under the implied liability that his use of it shall not be injurious to the general enjoyment of others having an equal right to the enjoyment of their property, nor injurious to the rights of the community. All property in this Commonwealth is . . . held subject to those general regulations which are necessary to the common good and general welfare. Rights of property, like all other social and conventional rights, are subject to such reasonable limitations in their enjoyment as shall prevent them from being injurious, and to such reasonable restraints and regulations established by law as the legislature, under the governing and controlling power vested in them by the Constitution, may think necessary and expedient. This is very different from the right of eminent domain, - the right of a government to take and appropriate private property whenever the public exigency requires it, which can be done only on condition of providing a reasonable compensation therefor.5 The power we allude to is may this interference be an arbitrary one. That is to say, in each case, the propriety of the interference may be questioned by the individual, and, when so questioned, the official whose act constitutes the interference must be able to justify his act by referring to a valid law and to some consideration of public necessity or convenience. If a person is drafted into military service, there must have been enacted a valid drafting law, including within its application the class of persons to which the individual drafted belongs. If a contract formally valid is refused enforcement, it must be shown to be opposed to public policy. If property is taken under eminent domain, it must be for a public use, and compensation must be given. If the rates charged by public service corporations are regulated by law, the regulation must be a reasonable one and not one, in its effect, confiscatory of private property. Finally, to constitute a valid exercise of the so-called police power of the State, there must be shown some public advantage to be gained by thus interfering with the personal liberty and property rights of the individual.

4 7 Cush. 53.

5 This requirement of compensation in the case of the appropriation of private property under the right of eminent domain, is created in this country rather the police power; the power vested in the legislature by the Constitution to make, ordain, and establish all manner of wholesome and reasonable laws, statutes, and ordinances, either with penalties or without, not repugnant to the Constitution, as they shall judge to be for the good and welfare of the Commonwealth, and of the subjects of the same. It is much easier to perceive and realize the existence and the sources of this power than to mark its boundaries, and prescribe the limits to its exercise." Hare, in his American Constitutional Law,6 says: "The police power may be justly said to be more general and pervading than any other. It embraces all the operations of society and government; all the constitutional provisions presuppose its existence, and none of them preclude its legitimate exercise. It is impliedly reserved in every public grant. Chartered rights and privileges are therefore like other property, held in subordination to the authority of the government, which may be so exercised as to preclude the use or doing of the very thing which the company was constituted or authorized to manufacture or perform. The legislature cannot be presumed to have intended to tie its hands in this regard in the absence of express words; but if such a purpose were declared, it would fail, as an attempt to part with an attribute of sovereignty which is essential to the welfare of the community."