342  Bark  of  Robinia  Pseudacacia.  Si*™' 
was  not  without  effect.  A  solution  of  the  same  substance,  when 
heated  sufficiently  to  coagulate  the  protein,  was  quite  devoid  of 
activity.  As  the  above  experiments  had  been  conducted  with  a 
bark  collected  by  myself  at  Madison,  Wisconsin,  it  may  be  noted 
that  some  years  subsequently  a  quantity  of  protein  material  was 
prepared  from  Robinia  bark  collected  in  France.  This  protein 
material,  when  isolated  by  the  simple  method  above  described,  pos- 
sessed the  same  toxic  properties  as  that  previously  obtained.  It  is 
well  known  that  substances  of  this  character  lose  their  activity  to 
a  greater  or  less  extent  on  keeping,  even  in  a  dry  state,  and  that 
they  also  undergo  change  in  this  respect  when  their  purification  is 
attempted  by  methods  of  repeated  solution  and  precipitation  or  by 
subjecting  them  to  dialysis.  Some  change  of  this  nature  may  have 
taken  place  in  the  material  employed  by  Professor  Kobert  for  his 
recent  experiments,  and  this  would  appear  to  be  the  most  probable 
explanation  of  the  results  now  obtained  by  him,  which,  moreover, 
are  so  completely  at  variance  with  his  own  earlier  observations.* 
As  a  specimen  of  the  Robinia  protein  which  had  been  prepared 
by  myself  in  1904  was  still  available,  it  was  deemed  of  interest  to 
ascertain  whether  it  still  retained  its  original  toxic  properties.  It 
was  therefore  kindly  tested  with  respect  to  its  activity  by  Dr.  H. 
H.  Dale,  Director  of  the  Wellcome  Physiological  Research  Labora- 
tories. An  amount  of  0.25  gramme  was  administered  by  the  mouth 
to  a  dog,  when,  after  an  interval  of  about  an  hour,  it  produced  two 
attacks  of  vomiting.  This  result,  together  with  the  observations 
previously  recorded,  as  noted  above,  clearly  demonstrate  that  the 
poisonous  constituent  of  Robinia  bark  is  a  protein.  They  cer- 
tainly lend  no  support  to  the  statement  of  Professor  Kobert  that 
the  respective  protein,  or  robin,  is  a  non-poisonous  "  phasin,"  or  to 
his  presumption  that  the  activity  of  the  bark  is  due  either  to  an 
alkaloid  or  a  glucoside. 
There  remains  to  be  considered  the  statement  of  Professor 
*  Since  writing  this  paper  I  have  been  favored  with  a  private  communica- 
tion from  Professor  Kobert,  in  which  he  informs  me  that  his  method  of 
testing  the  hydrolytic  action  of  robin  was  by  mixing  a  1  per  cent,  solution  of 
the  protein  with  a  1  per  cent,  solution  of  sinigrin,  and  observing  the  result 
after  keeping  the  mixture  for  some  time,  either  at  the  room  temperature  or 
at  a  temperature  of  380  C.  It  is  not  surprising  that  under  these  conditions 
no  odor  of  mustard  oil  was  perceptible.  Apart  from  the  extreme  dilution 
of  the  robin  solution  employed,  it  is  probable  that  in  the  preparation  of  the 
latter  the  active  portion  of  the  protein  had  been  removed. 
