68 
.  Purgative  action  of  Aloes. 
(  Am.  Jour.  Pharm 
I     Feb.  1, 1871. 
information  concerning  the  chemical  properties  of  the  drug,  and  we 
have  much  pleasure  in  bearing  testimony  to  the  ability  of  his  researches, 
but,  at  the  same  time,  we  feel  called  upon  to  notice  one  or  two  points 
in  his  paper,  on  which  we  conceive  his  deductions  to  be  erroneous. 
He  states  that  the  active  constituent  of  aloes  is  still  unknown  ; 
that  Robiquet  first  showed  that  the  purgative  property  was  not  due  to 
aloin  ;  and  he  asserts  that  this  latter  substance  is  in  complete  disuse. 
On  these  points  we  entertain  entirely  diverse  opinions,  and  as  the 
discoverers,  and  as  far  as  we  know  the  only  manufacturers  of  aloin, 
we  claim  to  some  little  knowledge  of  its  chemical  and  therapeutical 
properties. 
Mr.  Tilden  enumerates  and  describes  four  /substances  said  to  be 
present  in  aloes  of  the  best  quality,  viz. : — - 
(1.)    Aloetin,  aloesin,  amorphous  aloin,  bitter  principle  of  aloes. 
(2.)    Crystallized  aloin. 
(3.)  Resin. 
(4.)    Aloesic  acid. 
Of  these  four  Mr.  Tilden  disbelieves  in  the  existence  of  one,  viz. 
aloesic  acid,  and  adduces  a  reason  why  (3)  resin  should  be  related  to 
the  soluble  portion  of  aloes.  Of  aloetin  he  remarks  that  it  is  very 
important  as  to  quality,  and  there  can  be  no  doubt  it  is  the  product 
of  the  alteration  of  crystallized  aloin.  He  regards  it  as  a  mixture  of 
crystallized  aloin,  capable  of  recovering  its  crystalline  condition  in 
presence  of  water,  and  brown  oxidized  matter.  We  have  many  and 
various  reasons  for  at  present  coinciding  to  some  extent  with  Mr. 
Tilden  in  these  remarks,  but  we  are  entirely  at  a  loss  to  imagine  to 
what  substance  he  could  attribute  the  purgative  action  of  aloes,  since 
he  denies  that  aloin  has  any  such  effect,  and  yet  concludes  that  aloes 
absolutely  consists  of  that  substance  and  products  of  its  decomposi- 
tion. 
It  is  well  known  that  the  medicinal  powers  of  aloes  are  not  equal 
in  different  samples  ;  that  of  two  samples  of  the  same  variety,  one 
may  possess  twice  the  purgative  action  of  the  other,  and  that  when 
the  varieties  are  different,  the  difference  in  medicinal  value  is  in  many 
cases  even  more  marked. 
,^  The  idea  of  an  active  principle  is  generally  tenaciously  associated 
with  something  such  as  strychnia  or  aconitia,  of  infinite  power  in 
small  doses  ;  but  there  are  very  many  active  principles,  it  must  be  re- 
