270    INFLUENCE  OF  CULTIVATION  UPON  MEDICINAL  PLANTS. 
then  disappear  to  return  again  and  again  disappear ;  thus  obey- 
ing some  particular  physical  and  chemical  influences  which  are 
necessary  for  their  development. 
"  The  study  of  the  physical  and  chemical  causes  which  are 
concerned  in  the  distribution  of  plants  over  the  earth  constitutes 
the  science  of  Botanical  Geography.  It  is  upon  the  data  fur- 
nished by  this  science  and  upon  some  very  conclusive  physio- 
logical experiments  that  the  selection  of  medicinal  plants  should 
be  based  if  we  desire  to  obtain  efficient  remedies  ;  such,  at  least, 
is  the  design  of  pharmacologists  when  they  advise  the  employ- 
ment of  wild  plants,  for  they  think  that  when  they  are  obtained 
growing  under  other  conditions,  that  is,  when  in  a  state  of  cul- 
tivation, they  have  lost  a  great  portion  of  their  medicinal  prop- 
erties. 
"  It  is  unnecessary  for  us  to  refer  here  to  the  various  modifi- 
cations which  the  use  of  simples  in  medicine  have  undergone,  or 
to  the  value  of  the  more  or  less  whimsical  notions  which  led 
to  the  mixture  of  many  obscure  remedies  with  those  of  undoubted 
medicinal  value.  It  is  sufficient  for  us,  at  the  present  time,  to 
show  that  a  great  number  of  plants  do  possess  valuable  medicinal 
properties,  which  render  their  use  of  great  importance  in  the 
treatment  of  many  diseases  ;  and  that,  from  their  frequent  and 
daily  employment,  a  great  increase  in  the  commercial  value  of 
several  of  them  has  resulted.  Hence  has  arisen  the  idea  of  sub- 
mitting such  plants  to  cultivation  in  the  same  way  as  is  done 
on  a  large  scale  with  those  species  which  are  employed  for  food 
or  forage.  Such  attempts  were  at  first  made  on  a  small  scale, 
but  in  a  short  time  horticultural  establishments  arose  on  all  sides 
in  which  were  cultivated  all  our  indigenous  plants  employed  in 
medicine,  from  the  digitalis,  belladonna,  aconite,  etc.,  to  the 
mullein  and  common  red  poppy.  These  productions,  more  de- 
veloped, more  fattened,  if  I  may  so  speak,  by  cultivation,  sell, 
on  account  of  their  better  appearance,  etc.,  at  much  higher  prices 
than  the  same  obtained  in  a  natural  state. 
"  In  these  establishments  all  the  plants  are  grown  together 
without  any  previous  investigation  as  to  whether  the  soil  be 
favorable  or  otherwise ;  whether  the  situation  will  injure  the 
development  of  their  active  principles,  or  whether  the  height  of 
position  which  these  plants  prefer  will  not  result  in  modifying 
