544 
RESEARCHES  ON  ALOETIINE. 
istence  having  been  disputed,  I  have  not  taken  the  trouble  to 
place  crystallised  specimens  of  them  before  the  Academy  on  the 
present  occasion. 
In  1851,  Messrs.  Smith,  of  Edinburgh,  were  enabled  to  extract 
from  Barbadoes  aloes  a  crystallisable  body  to  which  they  gave 
the  name  of  alo'ine.  The  process  followed  by  these  chemists 
consisted  in  triturating  aloes  with  sand,  removing,  by  lixiviation, 
every  thing  that  is  soluble  in  cold  water,  and  evaporating  in  va- 
cuo, under  the  influence  of  a  temperature  of  50°  to  60Q  C.  (122° 
to  140°  F.) 
I  was  no  little  surprised  to  learn  this  result,  for  two  reasons : 
in  the  first  place,  this  mode  of  preparation  was  one  of  the  first  to 
occur  to  my  mind,  and  I  had  applied  it  in  vain  to  Socotrine  aloes ; 
and,  in  the  next  place,  being  of  opinion,  in  common  with  all  the 
authors  of  treatises  on  Materia  Medica,  that  transparent  and 
vitreous  Socotrine  aloes  is  the  best  of  all  kinds,  I  had  not  thought 
of  using  Barbadoes  or  hepatic  aloes.  Being  thus  punished  for 
my  excessive  confidence  in  the  statements  of  others,  I  very  soon 
returned  to  my  work.  My  first  care  was  to  repeat  Messrs. 
Smiths'  mode  of  preparation  on  Barbadoes  aloes,  and  on  vitre- 
ous Socotrine  aloes.  In  the  first  case,  I  obtained  crystals ;  in 
the  second,  a'n  amorphous  mass,  without  any  crystalline  appear- 
ance. 
I  then  dissolved  a  similar  quantity  of  Barbadoes  aloes  in  boil- 
ing water,  and  evaporated  the  solution  to  dryness,  on  a  sand 
bath,  in  the  open  air.  It  became  transparent  and  vitreous,  that 
is  to  say,  quite  similar  to  Socotrine  aloes  ;  but,  as  soon  as  this 
transformation  was  accomplished,  it  was  impossible  to  extract 
the  smallest  trace  of  crystals  from  it. 
The  mystery  was  then  cleared  up,  and  I  arrived  at  the  convic- 
tion that : 
1.  All  the  kinds  of  juices  of  vitreous  and  transparent  aloes 
(Socotrine  aloes,  Cape  aloes,  &c.)  have  undergone  the  action  of 
heat,  and  their  crystallisable  principle  is  metamorphosed  into  an 
amorphous  substance,  which  is  ordinarily  called  resin  of  aloes, 
but  which  is  no  other  than  aloetine,  which  has  become,  by  molec- 
ular change,  amorphous  aloetine,  insoluble  in  water. 
2.  All  the  kinds  of  opaque  aloes  with  a  waxy  fracture  were 
