MOLECULAR  DISSYMMETRY  OF  ORGANIC  PRODUCTS.  103 
VI. 
In  1850,  M.  Dessaignes,  whose  ingenious  skill  is  known  to 
chemists,  announced  to  the  Academy  that  he  had  succeeded  in 
transforming  the  bimalate  of  ammonia  into  aspartic  acid.  It 
was  a  step  which  tended  to  confirm  the  important  results  that 
M.  Piria  had  obtained  some  years  previously.  M.  Piria  had 
succeeded  in  transforming  asparagine  and  aspartic  acid  into 
malic  acid.  M.  Dessaignes,  in  his  turn,  showed  inversely  that 
malic  acid  could  be  re-formed  into  aspartic  acid. 
Thus  far  there  was  nothing  but  what  was  very  natural  in  the 
observation  of  M.  Dessaignes,  even  in  the  optical  point  of  view. 
For  my  part,  I  had  recognised  that  asparagine,  aspartic  acid, 
and  malic  acid,  were  active  on  polarized  light.  The  chemical 
passage  of  one  of  these  bodies  to  the  others  was  not  surprising. 
Some  months  later  M.  Dessaignes  made  another  step  forward. 
He  announced  that  not  only  the  bimalate  of  ammonia,  but  also 
the  fumarate  and  maleate  of  ammonia  had  equally  the  property 
of  being  transformed  by  heat  into  aspartic  acid. 
Here  I  perceived  an  impossibility  ;  or,  if  the  thing  was  as  M. 
Dessaignes  asserted,  this  skilful  chemist  had  made  a  discovery 
which  he  did  not  suspect.  Indeed,  I  observed  that  fumaric  and 
malic  acids,  and  all  their  salts,  were  without  action  on  polarized 
light.  If,  then,  M.  Dessaignes  had  succeeded  in  transforming 
their  salts  of  ammonia  into  aspartic  acid,  he  must  have  realized, 
for  the  first  time,  the  production  of  a  dissymmetric  body  by  the 
aid  of  compounds  which  are  not. 
But  it  appeared  to  me  more  reasonable  to  believe  that  the 
aspartic  acid  of  M.  Dessaignes  differed  from  natural  aspartic 
acid  decidedly  in  the  absence  of  the  molecular  rotary  property. 
M.  Dessaignes,  it  is  true,  had  carefully  compared  the  properties 
of  the  artificial  acid  with  those  of  the  natural  acid,  and,  as  he 
said,  found  them  identical.  Better  than  any  one,  from  the 
example  of  M.  Mitscherlich,  of  whom  I  spoke  at  our  last  meet- 
ing, I  knew  how  delicate  is  the  determination  of  the  identity  of 
chemical  species,  in  studies  in  which  the  greatest  similitude  of 
properties  often  conceal  profound  differences.  I  did  not  hesi- 
tate to  believe,  therefore,  that  the  new  fact  announced  by  M. 
Dessaignes  had  need  of  confirmation. 
I  attached  so  much  importance  to  the  elucidation  of  this 
