But while the idea expressed here that the human agents of commerce, in the sense of transportation, are instrumentalities of it, and so, in that capacity, within the protective power of Congress, signalized the entrance of Congress into the field of labor legislation, the Court was not at the time prepared to give the idea any considerable scope. Pertinent in this connection is the case of Adair _v._ United States,[407] which was decided between the two Employers' Liability Cases. Here was involved the validity of Sec. 10 of the "Erdman Act" of 1898,[408] by which it was made a misdemeanor for a carrier or agent thereof to require of an employee, as a condition of employment, that he should not become or remain a member of a trade union, or to threaten him with loss of employment if he should become or remain a member. This proviso the Court held not to be a regulation of commerce, there being no connection between an employee's membership in a labor organization and the carrying on of interstate commerce. Twenty-two years later, however, in 1930, the Court conceded that the connection between interstate commerce and union membership was a real and substantial one, and on that ground sustained the power of Congress in the Railway Labor Act of 1926[409] to prevent employers from interfering with the right of employees to select freely their own collective bargaining representatives.[410] The Railroad Retirement Act Still pursuing the idea of protecting commerce and the labor engaged in it concurrently, Congress, by the Railroad Retirement Act of June 27, 1934,[411] ordered the compulsory retirement of superannuated employees of interstate carriers, and provided that they be paid pensions out of a fund comprising compulsory contributions from the carriers and their present and future employees. In Railroad Retirement Board _v._ Alton R.R. Company,[412] however, a closely divided Court held this legislation to be in excess of Congress's power to regulate commerce and contrary to the due process clause of Amendment V. Said Justice Roberts for the majority: "We feel bound to hold that a pension plan thus imposed is in no proper sense a regulation of the activity of interstate transportation. It is an attempt for social ends to impose by sheer fiat noncontractual incidents upon the relation of employer and employee, not as a rule or regulation of commerce and transportation between the States, but as a means of assuring a particular class of employees against old age dependency. This is neither a necessary nor an appropriate rule or regulation affecting the due fulfillment of the railroads' duty to serve the public in interstate transportation."[413] Chief Justice Hughes, speaking for the dissenters, contended, on the contrary, that "the morale of the employees [had] an important bearing upon the efficiency of the transportation service." He added: "The fundamental consideration which supports this type of legislation is