Non-nitrogenous  proximate  principles  are  divided  into  two
groups — carbohydrates  (starch  and  sugar),  and  hydrocarbons  (fats) ;
the  latter  including  all  varieties  of  oleaginous  matter.
Starch. — During  mastication  starchy  matter  is  partly  converted
by  the  saliva  into  glucose,  which  has  during  digestion  the  same  sig-
nificance as  sugar.  Starch,  sugar,  and  fat  are  termed  non-nitrog-
enous because  they  contain  no  nitrogen,  but  consist  of  carbon,  hy-
drogen, and  oxygen — carbon  forming  44  to  84  per  cent.  Starchy
substances  are  converted  into  sugar  by  the  pancreatic  juice  also,
during  digestion.  The  necessity  and  desire  for  vegetable  food  is  so
great  that  restriction  to  a  diet  of  animal  food  would  surely  in  time
prove  fatal  to  the  .human  body.  Saccharine  and  oleaginous  sub-
stances are  necessary,  and  found  together  in  most  vegetable  food;  but
neither  is  alone  sufficient  for  nutrition.  In  a  short  time  health
would  fail  without  the  albuminous  and  fatty  proximate  principles.
Sugar. — The  sugar  in  the  food,  as  well  as  that  formed  in  the
liver,  disappears  by  decomposition  in  the  animal  fluids;  normally,
it  does  not  appear  in  any  of  the  excretions.  Sugar  contains  much
carbon,  which  may  be  demonstrated  by  placing  a  small  quantity
of  sugar  on  a  hot  stove;  the  water  evaporates  and  the  carbon
remains;  but  the  sweetness  of  the  sugar  is  destroyed,  as  its  mole-
cules are  split  up,  the  atoms  of  hydrogen  and  oxygen  having  sepa-
rated from  the  carbon.  Sugar  of  milk  and  liver  sugar  originate  in
the  body;  the  cells  of  the  mammary  gland  and  tho?e  of  the  liver,


28  NUTRITION.
