24 U.S.C. § 30 : US Code - Section 30: Payments to donors of blood for persons undergoing treatment at Government expense

      Any person, whether or not in the employ of the United States,
    who shall furnish blood from his or her veins for transfusion into
    the veins of a person entitled to and undergoing treatment at
    Government expense, whether in a Federal hospital or institution or
    in a civilian hospital or institution, or who shall furnish blood
    for blood banks or for other scientific and research purposes in
    connection with the care of any person entitled to treatment at
    Government expense, shall be entitled to be paid therefor such
    reasonable sum, not to exceed $50, for each blood withdrawal as may
    be determined by the head of the department or independent agency
    concerned, from public funds available to such department or
    independent agency for medical and hospital supplies: Provided,
    That no payment shall be made under this authority to any person
    for blood withdrawn for the benefit of the person from whom it is
    withdrawn.