That the following classes of aliens shall be excluded from admission into the United States: All idiots, imbeciles, feeble-minded persons, epileptics, insane persons: persons who have had one or more attacks of insanity at any time previously; persons of constitutional psychopathic inferiority; persons with chronic alcoholism; paupers . . . persons afflicted with tuberculosis in any form or with a loathsome or dangerous contagious disease; persons . . . mentally or physically defective . . . persons who have been convicted of or admit having committed a felony or other crime or misdemeanor involving moral turpitude; polygamists . . . anarchists . . . prostitutes . . . persons who directly or indirectly procure or attempt to procure or import prostitutes . . . contract laborers . . . persons likely to become a public charge; persons who have been deported under any of the provisions of this Act . . . persons whose tickets or passage is paid for with the money of another . . . stowaways . . . all children under sixteen years of age, unaccompanied by or not coming to one or both of their parents, except that any such children may, in the discretion of the Secretary of Labor, be admitted if in his opinion they are not likely to become a public charge and are otherwise eligible;