When  sensations  are  combined  in  other  cases,  as  red  and  blue-
green  to  produce  white,  or  partial  tones  to  form  a  compound,
we  either  cannot,  or  can  but  with  difficulty,  recognize  the
components;  in  this  case  the  person  feels  both  the  cold  and
l^ressure  distinctly  when  the  half-dollar  is  laid  on  him.
In  certain  cases  a  person  mistakes  the  contact  of  a  piece  of
raw  cotton  with  his  skin,  for  the  approach  of  a  warm  object;
this  has  been  taken  to  prove  that  touch  and  temperature  feel-
ings graduate  into  one  another.  However,  the  feeble  touch
of  the  raw  cotton  might  well  be  less  felt  than  the  increased
temperature  of  the  skin,  due  to  diminished  radiation  when  it
was  covered  by  this  non-conducting  substance ;  and  the  con-
stancy with  which,  in  the  ordinary  circumstances  of  life,  we
feel  and  discriminate  clearly,  on  the  same  skin  region  at  the
same  time,  both  temperature  and  touch  sensations,  is  a  strong
argument  against  any  transition  of  one  into  the  other.
