This  great  consideration  was  at  first  established  only  in  regard
to  anatomy ;  but  it  is  yet  more  necessary  in  physiology,  and  not
less  applicable,  except  from  the  difficulty  of  that  kind  of  observar
tion.  In  regard  to  physiological  problems  particularly,  it  should
be  remarked  that  not  only  all  animal  organisms,  but  the  vegetable
also,  should  be  included  in  the  comparison.  Many  important
phenomena,  and  among  others  those  of  organic  life,  properly  so
called,  can  not  be  analyzed  without  an  inclusion  of  the  vegetable
form  of  them.  There  we  see  them  in  their  simplest  and  most
marked  condition,  for  it  is  by  the  great  act  of  vegetable  assimilar
•tion  that  brute  matter  passes  really  into  the  organized  state,  all
ulterior  transformations  by  means  of  the  animal  organization  being
much  less  marked.  And  thus,  the  laws  of  nutrition,  which  are  of
the  highest  importance,  are  best  disclosed  by  the  vegetable  organ-
ism. The  method  is  unquestionably  applicable  to  all  organs  and
all  acts,  without  any  exception ;  but  its  scientific  value  diminishes
as  it  is  applied  to  the  higher  apparatus  and  functions  of  the  superior
organisms,  because  these  are  restricted  in  proportion  to  their  com-
plexity and  superiority.  This  is  eminently  the  case  with  the
highest  intellectual  and  moral  functions  which  below  Man  disap-
pear almost  entirely ;  or,  at  least,  almost  cease  to  be  recognisable
below  the  first  classes  of  the  mammifers.  We  can  not  but  feel  it
to  be  an  imperfection  in  the  comparative  method  that  it'  serves  us
least  where  we  are  most  in  need  of  all  our  resources  ;  but  it  would
be  unphilosophical  to  deprive  ourselves,  even  in  this  case,  of  the
light  which  is  cast  upon  the  analysis  of  Man  as  moral,  by  the  study
of  the  intellectual  and  affective  qualities  of  the  superior  animals,
and  of  all  others  which  present  such  attributes,  however  imperfect
our  management  of  the  comparison  may  yet  be.  And  we  may  ob-
serve that  the  comparative  method  finds  a  partial  equivalent  in  the
rational  analysis  of  ages, — thus  rendered  more  clear,  extensive,
and  complete, — ^for  the  disadvantages  which  belong  to  the  same
stage  of  the  biological  hierarchy.
