There  are  implied  limitations  upon  the  national  power  of  tax-
ation which  prevent  it  from  infringing  upon  the  governmental  func-
tions and  attributes  of  the  States.  The  United  States  is  not  supreme
in  this  respect,  but  its  government  and  those  of  the  several  states
occupy  a  position  of  equality,  except  so  far  as  the  latter  may  be
expressly  restricted  by  certain  provisions  of  the  Constitution.  The
doctrine  that  states  may  not  lay  taxes  upon  the  agencies  and  instru-
mentalities of  the  nation,  applies  in  the  same  manner,  to  the  same
extent,  and  for  the  same  reason,  to  the  exercise  of  the  taxing  power
by  the  United  States.  Congress  cannot  lay  a  tax  upon  any  of  the
agencies  or  instrumentalities  which  are  necessary  or  appropriate  for
the  legitimate  governmental  acts  and  operations  of  the  States.  Ap-
plying this  principle,  it  is  now  established  that  Congress  cannot
impose  an  income  tax  upon  the  salary  of  a  state  judicial  officer,  even
though  the  salary  is  not  subjected  to  the  impost  by  name,  but  the
statute  is  general  in  its  terms,  applying  to  all  incomes  greater  than
a  certain  specific  amount.^     In  accordance  with  the  same  principle;

1  Veazie  Bank  v.  Fenno,  8  Wall.  533.  2  Ibid.  p.  547.
»  Collector  v.  Day,  11  Wall.  113.
