AmjJa°nuy'i8P9?arm'}  Physiological  Action  of  Salicylic  Acid.  39 
natural  salicylic  acid  and  its  salt  of  sodium  in  proportionate  doses 
caused  no  bad  results. 
The  deductions  from  these  experiments  indicated  that  artificial 
salicylic  acid  and  its  salt  of  sodium  were  dangerous  to  animal  life, 
while  natural  salicylic  acid  and  its  salt  of  sodium  were  not. 
Further,  it  was  shown  that  the  difference  was  due  to  an  impurity 
in  the  artificial  acid,  not  a  trace  of  which  existed  in  the  natural 
salicylic  acid. 
This  impurity  was  observed  by  experiment  to  be  of  the  nature  of 
a  slow  but  certain  poison,  and  that  its  lethal  dose  was  relatively 
much  less  than  that  of  the  salicylic  acid  from  which  it  was  obtained. 
I  therefore  concluded  from  these  experiments  that  artificial  sali- 
cylic acid  contained  an  impurity  or  impurities,  and  that  until  this  or 
these  could  be  extracted  by  the  aid  of  chemistry,  the  internal 
administration  of  the  acid  or  its  salt  should  be  discountenanced.. 
Large  and  repeated  doses  of  the  sodium  salt  were  necessary  in  the 
treatment  of  acute  rheumatism,  and  hence  the  restlessness,  the  con- 
fusion and  the  delirium  attendant  at  times  on  their  use.  The 
retarded  convalescence  also  which  occurred  in  some  cases  of  acute 
rheumatism  after  the  salicylate  treatment  was  due  in  all  probability 
to  the  great  and  protracted  prostration  to  which  the  impurity  or 
impurities  gave  rise.  In  connection  with  these  symptoms  it  was 
noted  that  prescriptions  for  the  salicylate  of  sodium  were  invariably 
made  up,  unless  otherwise  indicated,  from  the  artificial  and  not  the 
natural  salt. 
The  conclusion  of  the  paper,  which  was  published  in  the  British 
Medical  Journal  of  November  30,  1S89,  was  "in  a  further  communi- 
cation we  will  state  the  physiological  action  of  the  acid  from  which 
the  impurity  has  been  removed." 
An  interval  of  some  months  elapsed  before  the  artificial  salicylic 
acid,  purified  by  Dr.  Henderson,  of  the  Chemical  Laboratory  of 
Glasgow  University,  was  submitted  to  the  physiological  test.  The 
result  was  disappointing.  We  found  that  it  caused  death  in  a  10 
grain  dose,  when  administered  to  a  full  grown  rabbit,  and  that  the 
same  thing  happened  when  a  sample  of  the  acid  of  a  Berlin  firm, 
guaranteed  pure,  was  tried  under  similar  conditions. 
In  the  paper  read  before  the  Royal  Medico-Chirurgical  Society 
on  February  14th,  I  entered  into  full  details  as  to  the  time  when  an 
article  by  the  late  Mr.  Williarns  was  brought  under  my  notice,  in 
