Where is IRS in Title 31 Organization

GEE Quatloos, I cant even find "Internal Revenue Service" in title 31 under Organization of the Department Of the Treasury! See 31 U.S.C. 301(f)(2): http://www.law.cornell.edu/uscode/31/301.html (f)(2) This is the ONLY mention of the IRS that I can find in the organization of the U.S. Treasury. Title 31 HAS been enacted into positive law.