But  this  loose  employment  of  the  term  "in
stinct"  really  accords  with  the  nature  of  the
thing;  for  it  is  wholly  impossible  to  draw  any
line  of  demarcation  between  reflex  actions  and
instincts.  If  a  frog,  on  the  flank  of  which  a  little
drop  of  acid  has  been  placed,  rubs  it  off  with  the


V         THE    MENTAL    PHENOMENA   OF    ANIMALS      131

foot  of  the  same  side ;  and,  if  that  foot  be  held,
performs  the  same  operation,  at  the  cost  of  much
effort,  with  the  other  foot,  it  certainly  displays  a
curious  instinct.  But  it  is  no  less  true  that  the
whole  operation  is  a  reflex  operation  of  the  spinal
cord,  which  can  be  performed  quite  as  well  when
the  brain  is  destroyed ;  and  between  which  and
simple  reflex  actions  there  is  a  complete  series  of
gradations.  In  like  manner,  when  an  infant
takes  the  breast,  it  is  impossible  to  say  whether
the  action  should  be  rather  termed  instinctive  or
reflex.
