102       MOLECULAR  DISSYMMETRY  OF  ORGANIC  PRODUCTS. 
Artificial  products,  then,  have  no  molecular  dissymmetry ;  I 
do  not  know  how  to  indicate  the  existence  of  a  more  perfect 
separation  between  the  products  originating  under  the  influence 
of  life  and  all  others.  We  insist  a  little,  because  you  will  see 
in  the  sequel  of  this  lecture  the  physiological  aspect  of  these 
studies  disengages  itself  more  and  more.  Let  us  pass  in  review 
the  principal  classes  of  natural  organic  products: 
Cellulose,  feculae,  gums,  sugars ;  tartaric,  malic,  quinic,  tan- 
nic acids;  morphia,  codeia,  quinia,  strychnia,  brucia  ;  essences  of 
turpentine,  of  lemon  ;  albumen,  fibrin,  gelatin.  All  these  im- 
mediate principles  are  molecularly  dissymmetric.  All  these 
substances  have  the  rotary  power  when  in  solution  ;  a  character 
necessary  and  sufficient  to  establish  their  dissymmetry,  even 
when,  in  the  absence  of  possible  crystallization,  hemihedrity 
would  be  wanting  for  the  recognition  of  this  property. 
All  the  substances  most  essential  to  the  vegetable  and  animal 
organism  figure  in  this  enumeration. 
There  are  many  natural  substances  which  are  not  dissym- 
metric. But  are  they  natural  in  the  same  sense  as  the  others  ? 
Do  we  not  necessarily  see  in  such  bodies  as  oxalic  acid,  hydruret 
of  salicyle,  fumaric  acid,  the  derivatives  of  natural  substances 
properly  so  called,  formed  by  actions  analogous  to  those  of  the 
laboratory  ?  These  products  seem  to  me  to  be  in  the  vegetable 
organism  what  urea,  uric  acid,  creatin,  glycocol,  are  in  the  ani- 
mal organism,  rather  excretions  than  secretions,  if  I  may  so 
speak.  It  will  be  very  interesting  to  follow  this  point  of  view 
experimentally. 
We  may  add  to  this,  that  many  bodies,  non-dissymmetric  in 
appearance,  may  be  paratartarics.  A  word  is  wanting  in  che- 
mical language  to  express  the  fact  of  a  double  molecular  dis- 
symmetry concealed  by  the  neutralization  of  two  inverse  dissym- 
metries, the  physical  and  geometric  effects  of  which  rigorously 
compensate  each  other. 
The  double  proposition,  to  which  we  have  just  been  led,  upon 
the  habitual  dissymmetry  of  immediate  organic  principles,  and 
upon  the  absence  of  this  character  in  all  the  products  of  inor- 
ganic nature,  enables  us  to  enlarge  and  render  more  and  more 
precise  our  manner  of  viewing  the  subject  of  this  remarkable 
molecular  property. 
