Generation  and  Expenditure  of  Bodily  Energy.  —  Still
another  means  of  influencing  cell  conditions  is  found  in  our
methods  of  using  bodily  energy,  or  power.  Our  energy  is  de-
rived from  different  kinds  of  foods  and  from  the  oxygen
which  we  breathe.  These  contain  energy  in  the  potential
or  latent  form,  somewhat  as  energy  is  associated  with  the


A   BASIS    FOR    CONTROL  17

water  in  a  pond  above  a  mill  dam  or  is  resident  in  gun-
powder or  dynamite.  This  energy  becomes  available  for
the  use  of  the  body  through  chemical  processes  that  take
place  in  the  cells.  The  oxygen  unites  with  the  elements
contained  in  the  food,  and,  in  so  doing,  transforms  the  po-
tential energy  into  kinetic,  or  active,  energy  which  is  then
expended  in  body  work.
Energy  Outlets. -- The  body  expends  energy  both  in-
ternally and  externally.  In  the  circulation  of  the  blood,
the  digestion  of  the  food,  breathing,  and  the  throwing
off  of  waste,  energy  is  spent  on  the  inside  and  in  ways
that  directly  pertain  to  the  welfare  of  the  cells.  In  mov-
ing the  body  from  place  to  place,  in  procuring  food,
clothing,  and  shelter,  and  in  bodily  adjustments  gen-
erally, energy  is  expended  through  external  channels.
One  outlet  for  energy  is  through  the  muscles,  another
is  through  the  brain,  and  a  third  is  through  the  organs
(glands)  that  manufacture  special  substances  needed  in
the  body.  Something  like  four-fifths  of  the  body's
energy  is  expended  as  heat.
Health  through  Energy  Control.  —  Certain  facts  re-
lating to  the  expenditure  of  energy  by  machines  are
applicable  to  the  energy  problem  of  the  body.  We
cannot  expend  more  energy  than  we  generate,  and  en-
ergy used  for  one  purpose  cannot  be  used  for  another.
