Am.  Jour.  Pharm. 
Nov.,  1921. 
£  Chemical  Elements  of  Living  Matter. 
749 
In  ionized  form,  as  phosphates  of  sodium  and  potassium,  it  main- 
tains the  neutral  reaction  of  blood  and  other  liquid  tissues  (buffer 
solution).  The  solid  phosphates  of  calcium  and  magnesium  are  pre- 
dominant in  the  skeletons  of  animals.  Small  doses  of  phosphorus 
stimulate  the  brain  and  circulation,  the  function  of  the  genital 
organs,  and  the  growth  of  bones.  Phosphorus  is  thus  the  regulating 
and  controlling  element  of  the  cell  metabolism. 
6.  Sulfur,  as  essential  constituent  of  the  proteins,  is  invariably 
present  in  animal  and  vegetable  organisms.  It  is  a  constituent  of  the 
aminoacid  cystin  and  so  occurs  in  keratin  or  the  epidermal  protein, 
in  connective  tissues,  in  taurocholic  acid  of  the  bile,  and  as  sulfates 
in  blood  and  other  liquors.  Free  sulfur  occurs  in  the  protoplasm  of 
certain  protozoa  or  unicellular  animals.  Hydrogen  sulfide  is  a  con- 
stituent of  the  intestinal  gases  of  vertebrates,  formed  together  with 
mercaptans  from  the  decomposition  of  proteins  rich  in  cystin.  Sul- 
focyanates  occur  in  saliva,  nose  secretions,  and  urine,  while  sulfuric 
acid  has  been  found  in  the  saliva  of  certain  snails  as  the  product  of 
bacterial  metabolism.  The  ash  of  plants  contains  on  an  average 
from  0.7—7%  of  S03. 
7.  Magnesium,  present  throughout  the  cell  organism,  occurs 
especially  as  magnesium  phosphate  in  bones,  teeth,  blood,  muscles 
and  nerves  of  the  vertebrates.  It  is  abundant  in  many  lower  animals 
(e.  g.,  corallinaceae) .  As  permanent  constituent  of  chlorophyll  it  is 
essential  to  the  metabolism  of  plants.  Aetiophyllin  C3iH34N4Mg, 
a  constituent  of  chlorophyll,  is  a  substance  closely  related  to  haemo- 
phyllin  of  the  haemoglobin  of  blood.  Magnesium  has  a  close  rela- 
tion to  phosphorus,  for  it  is  more  abundant  in  the  plant  parts  under- 
going development  (seeds  and  growing  tips)  and  is  absent  in  matur- 
ing organs.  Oily  seeds  contain  more  Mg  than  starchy  seeds, — by 
the  absence  of  Mg  no  oil  is  formed.  It  is  a  vehicle  for  the  assimila- 
tion of  phosphoric  acid  and  so  aids  indirectly  the  formation  of 
nucleoproteins. 
Content  of  MgO  in  the  Ash  of  Plants: 
100  parts  of  plant  ash  contain  MgO 
in  roots,  average 
in  stems,  average 
in  leaves,  average 
in  seeds,  average 
4-12% 
8-17% 
3-7% 
2-4% 
