Collector _v._ Day was decided in 1871 while the country was still in the throes of reconstruction. As noted by Chief Justice Stone in a footnote to his opinion in Helvering _v._ Gerhardt,[224] the Court had not then determined how far the Civil War amendments had broadened the federal power at the expense of the States; the fact that the taxing power had recently been used with destructive effect upon notes issued by State banks[225] suggested the possibility of similar attacks upon the existence of the States themselves. Two years later the Court took the logical further step of holding that the federal income tax could not be imposed on income received by a municipal corporation from its investments.[226] A far-reaching extension of private immunity was granted in Pollock _v._ Farmers Loan and Trust Co.,[227] where interest received by a private investor on State or municipal bonds was held to be exempt from federal taxation. As the apprehensions of this era subsided, the doctrine of these cases was pushed into the background. It never received the same wide application as did McCulloch _v._ Maryland[228] in curbing the power of the States to tax operations or instrumentalities of the Federal Government. Only once since the turn of the century has the national taxing power been further narrowed in the name of Dual Federalism. In 1931 the Court held that a federal excise tax was inapplicable to the manufacture and sale to a municipal corporation of equipment for its police force.[229] Justices Stone and Brandeis dissented from this decision and it is doubtful whether it would be followed today. FEDERAL TAXATION OF STATE INTERESTS