Subtitle IV of title 49, and the Safety Appliance Acts and the several amendments made or to be made thereto, shall not apply to Puerto Rico.
(Mar. 2, 1917, ch. 145, § 38, 39 Stat. 964; Mar. 4, 1927, ch. 503, § 6, 44 Stat. 1421; May 17, 1932, ch. 190, 47 Stat. 158.)