Am.  Jour.  Pharm. 
July,  1891. 
Artificial  Salicylic  Acid. 
365 
a  certain  time  under  such  conditions  the  virulence  is  found  to  have 
diminished.  Injections  of  the  virus  so  attenuated  not  only  confer 
immunity  against  rabies,  but  actually  prevent  its  development  even 
if  practised  after  the  disease  has  been  introduced  into  the  system 
by  the  bite  of  a  rabid  animal.  This  is  rendered  possible  by  the 
exceptionally  long  incubation  period  of  rabies. 
In  the  case  of  tuberculosis,  or  consumption,  the  method  employed 
is  somewhat  different,  although  it  is  probable  that  at  some  not  very 
remote  date,  the  principle  underlying  both  methods  may  be  shown 
to  be  the  same.  Koch  found  in  the  course  of  his  observations 
that  the  bacillus  of  consumption  when  injected  in  cases  of  con- 
sumptive affections  of  the  skin  produced  increased  activity  in  the 
regions  affected,  resulting  in  the  casting  off  of  the  affected  skin  and 
healing  of  the  scars.  By  a  series  of  masterly  experiments  and 
inductions  he  showed  that  it  was  not  the  bacillus  itself  which  pro- 
duced this  effect,  but  a  poison  secreted  by  it.  This  poison  he  suc- 
ceeded in  extracting  from  pure  cultures  of  the  bacillus  by  means  of 
a  mixture  of  glycerin  and  water,  and  this  is  the  fluid  which,  dur- 
ing the  last  few  months,  has  been  creating  such  a  stir  throughout 
the  whole  world.  Whether  the  remedy  will  do  all  that  news- 
paper correspondents  have  claimed  for  it  is  very  questionable; 
but  it  is  beyond  doubt  that  its  properties  are  most  remarkable, 
and  that  it  will  be  to  the  physician  a  most  powerful  auxiliary  in  the 
detection  and  treatment  of  some  of  the  most  insidious  diseases  to 
which  flesh  is  heir. — Phar.  Jour,  and  Trans.,  May  16,  p.  1019. 
ARTIFICIAL  SALICYLIC  ACID.1 
By  W.  R.  Dunstan  and  O.  F.  C.  Bloch. 
Artificial  salicylic  acid  has  been  observed  to  differ  in  its  thera- 
peutic action  from  the  pure  "  natural "  acid  obtained  from  the  oil  of 
winter-green.  Although  much  work  has  already  been  done  on  the 
subject  with  the  view  of  ascertaining  the  cause  of  this  difference, 
the  exact  nature  of  the  impurities  contained  in  the  artificial  acid  of 
commerce  has  not  been  experimentally  established.  The  authors 
have  examined  two  foreign  acids,  isolated  by  Williams  in  1878  from 
commercial  salicylic  acid,  but  not  then  identified.    These  acids  are 
1  Pharm.  J.  Trans.  [3],  21,  429 — 436,  abstract;  reprinted  from  Jour.  Chem. 
Soc,  1891,  454. 
