AmAui°ust  i9hi3rm' }       Bark  °f  Robinia  Pseudacacia.  343 
Robert  (loc.  ext.,  p.  83)  that  the  robin,  or  protein  material  pre- 
pared by  him  was  not  capable  of  hydrolyzing  sinigrin,  and  pos- 
sessed in  fact  no  hydrolyzing  action  on  glucosides,  nor  did  it  coagu- 
late milk.  His  failure  to  obtain  positive  results  in  these  experiments 
was  certainly  due  to  no  inaccuracy  in  my  observations,  as  would 
thereby  be  implied.  Since  the  receipt  of  his  publication  I  have 
again  tested  in  this  direction  the  above-mentioned  specimen  of 
robin  which  was  prepared  in  1904,  and  had  thus  been  kept,  in  well- 
stoppered  bottles,  for  a  period  of  nine  years.  This  material  was 
both  in  the  form  of  dark  brown  scales,  as  originally  obtained  on 
drying  the  precipitated  protein,  and  in  the  form  of  a  lighter-colored 
powder,  which  was  produced  at  the  same  time  by  triturating  the 
first  mentioned  product.  These  two  forms  of  the  preparation  were 
separately  tested,  both  with  amygdalin  and  with  a  well-crystallized 
specimen  of  sinigrin  (potassium  myronate)  in  the  following  man- 
ner: Into  a  small  test-tube,  provided  with  a  well-fitting  cork,  was 
brought  a  small  quantity  of  the  respective  glucoside,  together  with 
some  of  the  dry  protein,  and  a  little  water  subsequently  added.  The 
tubes  being  then  corked,  and  the  mixtures  vigorously  shaken,  they 
were  set  aside  at  the  ordinary  temperature  (16-180  C.)  and  occa- 
sionally agitated.  After  a  period  of  about  24  hours  or  less  the 
tubes  were  opened,  when  in  the  one  case  there  was  a  strong  odor 
of  bitter  almond  oil,  and  in  the  other  an  equally  distinctive,  sharp 
odor  of  mustard  oil.  The  unmistakable  results  of  these  tests,  which 
are  doubtless  obtained  much  more  quickly  with  the  fresh  Robinia 
protein,  thus  not  only  confirmed  my  previous  observations,  but  they 
have  now  also  been  confirmed  independently  by  five  chemists  in 
these  laboratories.  It  was  not  deemed  necessary  to  again  repeat 
the  test  with  milk,  the  coagulation  of  which  by  the  protein,  or  an 
enzyme  therein  contained,  I  had  previously  fully  and  accurately 
described. 
The  properties  which  the  protein  material  designated  as  "  robin  " 
has  been  shown  to  possess  renders  it  probable  that,  like  other  similar 
products,  it  is  a  mixture  of  substances,  but  no  method  is  known  to 
the  present  author  by  means  of  which  a  separation  of  its  constit- 
uents could  be  effected  without  a  corresponding  loss  of  activity. 
It  is  also  not  known  whether  the  toxic  action  of  the  protein  is  due 
to  a  substance  which  at  the  same  time  possesses  enzymic  proper- 
ties, but  as  the  last-mentioned  properties  are  so  varied  in  character, 
no  doubt  can  be  entertained  respecting  the  presence  of  several 
