But by far the most notable of these safety measures were the Federal Employers Liability Acts of 1906 and 1908,[404] the second of which merely reenacted the first with certain "unconstitutional" features eliminated. What the amended act does, in short, is to modify, in the case of injuries incurred by the employees of interstate carriers while engaged in interstate commerce, the defenses that had hitherto been available to the carriers at common law. The principal argument against the acts was that the commerce clause afforded no basis for an attempt to regulate the relation of master and servant, which had heretofore in all cases fallen to the reserved powers of the States; that indeed the rules of common law modified or abrogated by the act existed solely under State authority, and had always been enforced, in the main, in the courts of the States.[405] Countering this argument, the Court, speaking by Justice Van Devanter, quoted the following passage from the brief of the Solicitor-General: "Interstate commerce--if not always, at any rate when the commerce is transportation--is an act. Congress, of course, can do anything which, in the exercise by itself of a fair discretion, may be deemed appropriate to save the act of interstate commerce from prevention or interruption, or to make that act more secure, more reliable or more efficient. The act of interstate commerce is done by the labor of men and with the help of things; and these men and things are the agents and instruments of the commerce. If the agents or instruments are destroyed while they are doing the act, commerce is stopped; if the agents or instruments are interrupted, commerce is interrupted; if the agents or instruments are not of the right kind or quality, commerce in consequence becomes slow or costly or unsafe or otherwise inefficient; and if the conditions under which the agents or instruments do the work of commerce are wrong or disadvantageous, those bad conditions may and often will prevent or interrupt the act of commerce or make it less expeditious, less reliable, less economical and less secure. Therefore, Congress may legislate about the agents and instruments of interstate commerce, and about the conditions under which those agents and instruments perform the work of interstate commerce, whenever such legislation bears, or in the exercise of a fair legislative discretion can be deemed to bear, upon the reliability or promptness or economy or security or utility of the interstate commerce act."[406] The Adair Case