370  Standardization  of  Solid  Extracts.  {Amj'uiy?i896arm' 
foreign  to  the  drug  are  introduced,  and  it  becomes  a  simple  problem 
for  calculation  in  order  to  ascertain  the  proportions  of  the  weaker 
and  the  stronger  extracts  to  be  mixed  to  produce  an  extract  of 
standard  strength. 
In  the  case  of  some  solid  extracts  (such  as  belladonna)  which  con- 
tain a  large  amount  of  chlorophyll,  the  difficulty  is  often  experienced 
of  having  that  substance  separate  out  in  lumps  or  clots  as  the 
extract  nears  completion.  It  can  rarely,  if  ever,  be  thoroughly 
incorporated  so  as  to  make  a  perfectly  homogeneous  extract ;  and 
while  it  is  possible  to  remove  this  separated  chlorophyll  without 
impairing  the  medicinal  activity  of  the  preparation,  the  extract  does 
not  then  possess  the  color  which  is  characteristic  to  it,  and,  in  the 
case  of  extract  of  belladonna,  resembles  the  preparation  made  from 
the  root  rather  than  that  made  from  the  leaf. 
This  difficulty  can  only  be  obviated  with  certainty  by  evaporating 
the  percolate  from  the  drug  under  reduced  pressure  with  continuous 
stirring,  which  is  impracticable  for  manufacturers  of  small  quantities. 
The  powdered  extracts  may  be  made  to  conform  to  fixed 
standards  in  the  same  manner  as  the  solid  extracts,  and  present  indi- 
cations show  that  but  a  short  time  will  elapse  until  standardized 
extracts,  both  solid  and  powdered,  will  be  the  rule  rather  than  the 
exception. 
Changes  of  a  radical  nature  must  necessarily  be  slow  in  order  to 
be  effective.  The  introduction  of  the  class  of  preparations  known 
as  abstracts  into  the  1880  Pharmacopoeia  was  too  abrupt.  They 
were  but  little  used,  and  were  dismissed  from  the  last  revision  of 
that  work.  This  was  not  due  to  lack  of  efficiency  in  any  respect, 
for  their  uniformity  rendered  them  preferable  to  the  powdered  ex- 
tracts, which  they  closely  resembled,  and  the  use  of  which  they  did 
not  seem  to  influence  in  the  least;  yet,  if  but  one  or  two  of  the 
more  important  abstracts  had  been  admitted  at  first,  it  might  have 
paved  the  way  for  the  permanent  introduction  of  one  of  the  most 
desirable  classes  of  preparations  the  Pharmacopoeia  has  ever  con- 
tained. 
A  list  is  given  below  of  the  yield  of  solid  extract  obtained  from  a 
number  of  drugs,  both  official  and  otherwise,  working  upon  a  large 
scale  in  practice.  These  figures  may  serve  as  additional  data  for 
other  workers  in  the  same  line,  and  the  author  hopes  that  the 
subject  of  the  standardization  of  the  solid  extracts  will  be  given 
