748 
Chemical  Elements  of  Living  Matter,  j 
Am.  Jour.  Pharm. 
Nov.,  1921. 
To  the  cell  metabolism  oxygen  is  the  element  which  burns  up  the 
waste-products  and  oxidizes  food  materials  thereby  liberating  the 
stored  energy  in  the  form  of  heat. 
4.  Nitrogen,  the  apparent  inert  and  lazy  gas  of  the  atmosphere, 
is  the  element  giving  instability  and  therefore  reactivity  to  organic 
compounds.  Nitrogen  can  form  several  series  of  compounds  which 
are  more  or  less  readily  transformed  into  each  other.  Thus  there 
are  the  compounds  of  the  lowest  valence  number  ( — 3)  or  com- 
pounds derived  from  ammonium  (NH3),  to  this  class  belong  the 
amino  acids  (NH2-R-COOH)  which  are  the  bricks  or  building 
stones  of  the  proteins.  The  next  series  of  compounds  are  derived 
from  nitrous  oxide  (N203)  with  a  valence  number  of  +3  and  in 
this  series  there  are  the  nitrites,  which  are  readily  oxidized  to 
nitrates.  Finally  the  compounds  derived  from  nitric  oxide  (N205; 
form  the  nitrates  (valence  number  +5)  and  are  the  highest  stage 
of  oxidation.  Nitrates  are  important  as  fertilizers  from  which  the 
plant  synthesises  the  complex  proteins  by  reducing  processes.  Nitro- 
gen forms  with  C,  H,  and  O  a  number  of  important  radicals  and 
compounds,  its  role  in  the  cell-metabolism  seems  to  be  the  imparting1 
of  instability  and  sensitiveness  to  protoplasmic  compounds. 
5.  Phosphorus,  the  controlling  element,  is  indispensable  to  the 
nucleus  of  the  cell.  It  occurs  in  nucleins,  lecithins,  and  vitellins ;  is 
essential  for  nerve  and  brain  cells  of  animals,  and  accumulates  in 
seeds  and  buds  of  plants.  It  is  a  constituent  of  chromatin,  the  in- 
tranuclear germ  plasm,  which  is  supposed  to  be  the  seat  of  heredity.4 
It  is  essential  in  the  assimilation  of  fats  which  are  transformed  into 
lecithins  before  assimilation  and  seems  to  accumulate  in  those  parts 
of  the  cell-organism  where  the  important  function  of  cell-division 
is  performed : 
Content  of  F2O5  in  the  Ash  of  Plants: 
100  parts  of  plant  ash  contain  P2O5 
in  stems 
in  leaves 
in  seeds 
m  roots  average 
12-17% 
4-12% 
9-13% 
37-49% 
4  Osborn,  Or'gin  and  Evolution  of  Life ;  N.  Y.,  1917 ;  page  21  ff. 
