The  salts  of  the  lactic  acid  from  flesh  differ  in  the  amount  of
water  of  crystallisation  from  those  of  the  acid  from  milk.
Lactic  acid  may  be  regarded  as  a  coupled  formic  acid,  the
copula  being  aldehyde ;  for  C«  H  Oe  (the  half  of  lactic  acid)  =
€2  H2  04  +  C*  H*  02 .  This  constitution  has  been  rendered  pro-
bable, by  the  discovery  that  lactic  acid  may  be  artificially  formed


STAECH.  451

from  alanine,  a  base  obtained  by  the  action  of  hydrocyanic  and
hydrochloric  acids  on  aldehydammonia.  It  is  well  known  that
hydrocyanic  acid  with  hydrochloric  acid  yields  formic  acid  and
ammonia.  In  the  above  reaction,  therefore,  we  have  formic  acid
and  aldehyde  in  statu  nascenti.  They  probably  combine  to  form
lactic  acid,  but  ammonia  being  also  present,  another  reaction
ensues,  and  alanine,  a  body  isomeric  with  lactamide,  is  obtained.
We  have  thus,  first,  €2  H2  0*  -f  C*  H*  02  =  Cs  He  Oe ;  and  then
C6  H6  06  +  N  H3  =  2  H  0  +  Ca  H7  NO*.  The  latter  group
is  alanine,  which,  when  acted  on  by  hyponitrous  acid,  yields  lactic
acid,  thus ;  Ca  N  H/  0*  +  N  Os  =  Ce  He  Oe  +  H  0  +  Na.
If  such  be  the  true  constitution  of  lactic  acid,  we  should  expect
it,  as  well  as  alanine,  to  be  one  of  a  homologous  series.  And,  in
fact,  this  is  the  case.  An  acid  has  been  discovered,  gly colic  acid,
C*  H*  Oe ,  which  is  formic  acid,  €2  Efo  0* ,  coupled  with  formic
aldehyde,  02  Ha  02 ;  and  glycocine,  C*  N  Hs  0* ,  is  the  compound
homologous  with  alanine,  and  corresponding  to  the  new  acid.
