AmNo°vU%878arm  }  Botanical  Characters  of  Offiicinal  Plants.  531 
It  is  not  my  intention  to  review  the  work  of  DeCandolle,  but  only 
to  investigate  some  parts  of  the  above  interesting  question,  especially 
in  regard  to  the  limit  of  comparison  which  should  be  observed  between 
the  plants  and  the  relative  properties  of  their  natural  orders. 
All  authors  accept  as  limit  of  comparison  between  plants  the  action 
which  they  exert  on  the  animal  organism.  DeCandolle  found  this 
view  of  the  question  deficient,  but  the  state  of  chemistry  at  his  time 
warranted  no  other  conclusion. 
To  establish  an  analogy,  a  well-defined  boundary  must  be  fixed  upon, 
which  in  this  study  cannot  be  done  by  examining  simply  the  properties 
of  plants,  but  rather  the  nature  and  properties  of  their  principal  consti- 
tuents. 
All  really  medicinally  active  plants  contain  substances  which,  in  most 
cases,  have  been  isolated  and  chemically  studied.  These  substances 
do  not  always  embrace  the  entire  properties  of  the  vegetable  from 
which  they  are  obtained.  On  the  contrary,  it  frequently  occurs  that 
the  greatest  diversity  exists  in  their  respective  actions.  The  cause  of 
this  seeming  anomaly  is  generally  due  to  the  fact  that  the  activity  of  a 
plant  represents  the  action  of  several  bodies  possessing  different  pro- 
perties ;  therefore  the  action  exerted  on  the  animal  organism  by  the 
vegetable  is  the  result  of  different,  sometimes  even  opposite,  influences. 
This  also  makes  the  strongest  point  against  the  too  eager  endeavor  of 
modern  therapeutics  to  replace  all  plants  by  their  active  principles  ;  it 
is  also  the  principal  cause  of  the  difficulty  met  in  the  systematic  classi- 
fication of  the  simple  medicinal  plants  according  to  their  properties. 
The  importance  of  the  chemical  study  of  plants  increases  daily  ;  it  is 
the  base  of  rational  Materia  Medica.  Analysis  is  the  only  safeguard 
against  the  flooding  of  pharmacv  by  innumerable  plants,  which,  to 
maintain  in  or  introduce  into  it,  would  intere%t  only  charlatanism  or 
ignorance.  An  officinal  plant,  whose  constituents  are  not  known,  is 
nothing  better  than  an  empyrical  remedy. 
A  very  important  fact  which  must  be  borne  in  mind  is  that  the  pro- 
perties of  the  indisputably  active  constituents  are  not  solely  dependent 
upon  the  proportion  of  the  elements  united  in  their  composition,  but 
also  on  their  molecular  constitution.     Bodies  may  be  isomeric,  have 
that  the  mal<vace<e  are  mucilaginous ;  that  the  crucifera  show  "  a  remarkable  simi- 
larity in  their  therapeutical  properties  j"  that  ^the  loganiacea?  contain  a  poisonous 
principle — in  short,  a  large  number  of  facts  supporting  the  theory  of  Linnaeus. 
