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Even when declared by a municipal corporation, it seems, like the punishment of criminals by city courts, more a public act than a strictly municipal one. By the very necessity of the case, a judi- cial inquiry to determine the propriety of declaring the quarantine is impracticable. The inquiry usually has to be conducted under circumstances in which judicial evidence cannot be had, and hearsay is the only available information. To admit witnesses from the region suspected to be infected, or to conduct an exam, ination of goods coming therefrom, would be to invite the very danger feared. In most cases action must be prompt, or it will be futile.
Turning now to the classification of quarantine laws in our con- stitutional law, we shall find these laws to belong both to the class of police regulations and the class of regulations of commerce. From the beginning there are few prominent cases in which the police power has been discussed, in which quarantine laws have not been treated as typical examples of its exercise. Just what is meant by the expression ** police power " is not difficult to fletermine, although an exact definition is impossible at the present stage of development of constitutional law. The Supreme Court has said : " This power is, and must be from its very nature, incapable of any very exact definition or limitation."^ The conception of police power, however, gradually becomes more definite. Cer- tainly no one would now say with Chief Justice Taney, that the police powers of a State " are nothing more or less than the pow- ers of government inherent in every sovereignty to the extent of its dominions," ^ although a recent opinion of the Supreme Court uses the term ** police powers " to signify ** the reserve powers of the State." ^ Perhaps the most satisfactory brief description is Judge Cooley's : " The police of a State, in a comprehensive sense, em- braces its whole system of internal regulation, by which the State seeks not only to preserve the public order and to prevent offences against the State, but also to establish for the intercourse of citi- zens with citizens those rules of good manners and good neighbor- hood which are calculated to prevent a conflict of rights, and to insure to each the uninterrupted enjoyment of his own, so far as is
��1 The SUughter-House Cases, 16 Wall 36, 62 (1872).
« The License Cases, 5 How. 504, 583 (1847).
» W. U. Telegraph Co. t/. Pendleton, 122 U. S. 347, 359 (1886).
