of  Animals  and  Vegetables . $ 
heat,  either  by  external  applications,  or  difeafe.  How- 
ever, thefe  variations  are  much  greater  below  the  ftan- 
dard  heat  than  above  it;  the  perfect  animals  having  a 
greater  power  of  refilling  heat  than  cold,  fo  that  they 
are  commonly  near  their  ultimate  heat.  Indeed  we  do 
not  want  any  other  proof  of  this  variation  than  our  own 
feelings : we  are  all  fenfible  of  heat  and  of  cold,  which 
fenfations  could  not  be  produced  without  an  alteration 
really  taking  place  in  the  parts  affected;  which  alteration 
in  the  parts  could  not  take  place,  if  they  did  not  become 
actually  warmer  or  colder.  I have  often  cooled  my 
hands  to  fuch  a degree,  that  I have  put  them  into  pump- 
water,  immediately  pumped,  to  warm  them ; therefore, 
my  hands  were  really  colder  than  the  pump-water. 
Real  increafe  of  heat  mull  alter  the  texture  or  pofition 
of  the  parts,  fo  as  to  produce  the  fenfation  called  heat : and 
as  this  heat  is  diminilhed,  the  texture  or  pofition  of  the 
parts  is  altered  in  a contrary  way ; which,  when  carried 
to  a certain  degree,  becomes  the  caufe  of  the  fenfation  of 
cold.  Now  thefe  effects  could  not  take  place  in  either 
cafe  without  a real  increafe  or  decreafe  of  heat  in  the 
part;  heat,  therefore,  in  its  different  degrees,  muft  be 
prefent.  When  heat  is  applied  to  the  Ikin,  it  becomes 
hot,  in  fome  degree,  according  to  the  application;  and 
this  may  be  carried  fo  far  as  actually  to  burn  the  living 
Vol.  LXVIIL  C parts: 
