2  Pharmacological  Assay  of  Drugs.  {ATanua?yfi902m* 
materia  medica  only  these  three  drugs,  all  of  which  owe  their 
activity  to  the  presence  of  alkaloids  in  some  quantity;  and  if  the 
method  be  extended  in  the  forthcoming  edition,  it  is  probable  that 
only  drugs  containing  alkaloids,  such  as  the  belladonna  group,  will 
be  embraced  by  it.  Those  plants  which  owe  their  activity  to  the 
presence  of  glucosides  will  undoubtedly  be  omitted.  Yet  the  prepa- 
rations of  some  of  these  are  in  constant  use  in  therapeutics  and 
have  to  be  given  in  quantities  which  approach  the  therapeutic 
maximum  and  stand  on  the  threshold  ot  the  poisonous  dose.  I 
need  refer  only  to  digitalis,  squill  and  strophanthus  to  illustrate 
this  point.  It  is  obviously  of  the  first  importance  that  the  prepa- 
rations of  these  drugs  should  be  of  uniform  strength,  and  yet  it  is 
notorious  that  they  vary  within  wide  limits.  For  example,  Jacquet 
found  the  strength  of  some  tinctures  of  digitalis  four  times  that  of 
another,  prepared  by  a  different  manufacturer,  although  all  were 
presumably  formed  according  to  the  same  directions.  I  have  not 
observed  such  marked  divergence  in  strength,  but  have  found  a 
difference  of  50  per  cent,  in  different  tinctures.  I  think  there  can 
be  no  doubt  that,  if  a  patient  treated  with  efficient  doses  of  the 
weakest  ot  Jacquet's  tinctures  were  subsequently  treated  with  the 
same  amount  of  the  strongest  (as  might  very  well  happen),  the 
effects  would  almost  certainly  be  alarming  and  might  be  disastrous. 
One  result  of  this  variation  in  the  strength  of  the  preparations  of 
these  drugs  has  been  the  use  of  the  so  called  principles,  such  as  the 
various  digitalins  and  strophanthins ;  I  have  examined  a  large 
number  of  these  and  have  found  them  vary  even  more  than  the 
galenical  preparations.  Some  of  them,  notably  the  more  attractive 
crystalline  forms,  were  entirely  inert,  while  others  were  extremely 
poisonous.  In  short,  they  require  to  be  standardized  as  much  as 
the  galenical  preparations.  But  if  there  can  be  no  question  as  to 
the  desirability  of  assaying  the  glucosidal  preparations,  there  is 
unfortunately  no  less  doubt  of  its  unpracticability  by  ordinary 
chemical  methods.  If  proof  of  this  were  lacking,  it  has  been  sup- 
plied by  the  painstaking  investigations  on  which  Kiliani  has  been 
engaged  for  so  many  years.  A  continuous  series  of  publications 
has  issued  from  his  laboratory  since  1892,  yet  only  in  1899  he 
recognized  a  glucoside  already  described  by  Schmiedeberg,  but 
overlooked  by  Kiliani  in  all  his  previous  work.  It  is  obviously 
impossible  to  assay  the  tincture  of  digitalis  by  isolating  each  gluco- 
