MOLECULAR  DISSYMMETRY  OF  ORGANIC  PRODUCTS.  101 
a  proper  dissymmetry,  which  is  translated  in  the  form  of  the 
crystal.  When  the  crystal  is  destroyed  by  solution,  there 
results  from  it  a  liquid  active  for  polarized  light,  because  it  is 
formed  of  molecules  pell-mell,  it  is  true,  but  each  having  a  dis- 
symmetry in  the  same  direction,  if  not  of  the  same  intensity  in 
all  directions. 
V. 
Quartz,  then,  is  not  molecularly  dissymmetric,  and  up  to  the 
present  time  we  do  not  know  any  example  of  a  mineral  which 
possesses  molecular  dissymmetry.  I  have  said  that  we  must 
extend  this  proposition  to  the  artificial  compounds  of  labora- 
tories. Here  still  we  may  have  some  scruples.  We  may 
object,  for  example,  that  native  camphor,  which  is  dissymmetric, 
yields  artificially  camphoric  acid,  also  dissymmetric  ;  that 
aspartic  acid  derived  from  asparagine  by  a  reaction  in  the 
laboratory  is  dissymmetric  like  asparagine,  and  I  might  cite 
many  other  like  examples.  But  no  one  doubts  that  camphoric 
and  aspartic  acids  owe  to  camphor  and  to  asparagine  their  proper 
dissymmetry.  This  exists  in  the  mother  products,  and  it  is 
transferred,  modified  more  or  less  by  substitution,  from  the 
mother  products  to  their  derivatives.  We  are  unable  to  pro- 
duce better  evidence,  in  general,  of  the  preservation  of  the 
primitive  type  in  a  series  of  products  connected  by  a  common 
origin,  than  the  permanence  of  the  optic  property. 
When  I  affirm  that  no  artificial  substance  has  yet  pre- 
sented molecular  dissymmetry,  I  mean  to  speak  of  artificial 
substances,  properly  so  called,  formed  entirely  of  mineral  ele- 
ments or  derived  frcm  non-dissymmetric  bodies.  For  example  : 
Alcohol  is  not  dissymmetric.  Its  molecule,  if  we  could  isolate 
and  study  it,  placed  before  a  mirror,  would  present  an  image 
superposable  to  it.  Now,  there  is  no  derivative  from  alcohol 
which  is  not  dissymmetric.  I  could  multiply  examples  of  this 
kind  without  end.  Further,  take  any  dissymmetric  body,  and 
if  you  subject  it  to  somewhat  energetic  chemical  reactions,  you 
will  assuredly  see  the  dissymmetry  of  the  primitive  group  dis- 
appear. Thus,  tartaric  acid  is  dissymmetric.  Pyrotartaric 
acid  is  no  longer  so.  Malic  acid  is  dissymmetric.  Maleic  and 
paramaleic  acids  of  M.  Pelouze  are  not.  Gum  is  dissymmetric, 
mucic  acid  is  not. 
