362 
Histology  of  Avar  aha. 
/  Am.  Jour.  Pharm-. 
\      July,  1880. 
prising  the  woody  column,  from  within  the  bark  to  the  medulla,  is. 
involved  in  the  decomposition,  which  results  in  the  formation  of 
araroba. 
The  next  question  that  occurred  was,  what  was  the  physical  condi- 
tion of  this  substance  immediately  resulting  from  the  destruction  of 
tissue  ?  The  araroba  was  found  to  have  permeated  more  or  less  and 
imbued  with  color  all  the  tissues,  even  those  which  retained  their  form,, 
but  it  filled  many  of  the  porous  vessels,  as  shown  in  No.  2,  and  whilst 
examining  under  a  high  power  the  deposit  in  one  of  these  vessels 
remains  of  cell  tissue  were  visible,  so  disposed  as  to  convey  the  impres- 
sion that  the  deposit  must  have  once  been  in  a  fluid  condition ;  and 
subsequent  examination  of  sections  from  different  pieces  of  wood^ 
taken  at  random  from  a  parcel  of  powder,  presented  other  indications 
leading  to  the  same  conclusion. 
It  will  be  observed  that  the  libriform  cells,  on  one  part  of  the 
section,  pressing  closely  upon  each  other,  are  in  their  outline  sharply 
polygonal,  whilst  at  the  other  they  are  separating,  and  show  indications 
of  having  been  subjected  to  some  solvent  action;  the  cells  have  lost 
their  polygonal  outline  and  are  gradually  becoming  loose  and  shapeless^ 
and  this  is  seen  rather  on  the  outside  in  contact  with  the  powder  than 
in  the  interior  of  the  wood.  It  is  difficult  also  to  understand  how  the 
porous  vessels  in  the  interior  of  the  wood  could  have  been  so  densly 
filled,  unless  the  araroba  had  been  in  a  fluid  or  semifluid  condition. 
That  its  presence  in  these  porous  vessels  is  not  due  to  decomposition 
of  the  vessels  themselves  is  evident  from  the  fact  that  when  the  con- 
tents are  removed  by  solution  and  the  cell  wall  examined  it  is  found  ta 
be  intact.  Did  the  araroba  consist  of  finely  comminuted  cell  tissue 
the  action  of  caustic  alkali  would  little  affect  it;  but  the  solution  of 
about  80  per  cent,  proves,  that  the  cell  tissue  has  been  changed  to  some 
other  substance  soluble  in  caustic  alkali.  So  far  as  these  investigations- 
go  they  point  to  a  fluid  condition  of  araroba,  whilst  its  presence  in  the 
clefts  and  hollow  places  of  the  wood,  and  the  fact  of  more  being  found 
in  old  trees  than  in  younger  ones,  must  dispose  at  once  of  the  idea  of 
its  being  a  secretion. 
The  most  interesting  point  of  the  inquiry  next  suggested  itself,  the. 
cause  of  this  formation.  On  this  point  there  is  no  satisfactory  evi- 
dence; but  araroba  has  its  analogies  in  the  gums  and  resins,  and  to  the. 
student  of  materia  medica  these  obscure  changes  in  plant  organism  are 
of  especial  interest.    Kutzing  first  observed  structure  in  tragacanth,. 
