Am.  Jour.  Pharm.  > 
July,  1880.  I 
Histology  of  A  r  or  aba. 
361 
vessels,  surrounded  by  the  parenchyma,  of  the  woody  tissue,  having 
•some  of  its  cells  thickened  and  dotted,  and  d  the  libriform  cells.  This 
■comprises  the  whole  of  the  cell  tissue  of  the  wood  yielding  araroba. 
The  drawing  No.  3  is  a  longitudinal  section  through  the  medullary 
and  libriform  cells,  showing  the  latter  disposed  in  their  length  as  elon- 
gated pointed  cells ;  the  several  ceils  composing  these  tissues  were 
isolated  and  identified. 
The  first  question  that  presented  itself  was, 
what  tissues  are  involved  in  the  formation  of 
araroba  }  Under  the  microscope,  either  alone 
or  in  any  fluid  that  does  not  change  its  nature, 
araroba  presents  the  character  of  an  amorphous 
powder;  by  heating  it  in  a  test  tube  in  a  solu- 
tion of  caustic  alkali,  which  dissolves  about  80 
,per  cent.,  it  was  hoped  that  some  indication 
would  be  obtained,  in  the  deposit,  of  cell  tissues, 
but  the  result  was  not  satisfactory.  Recourse 
was  then  had  to  boiling  in  repeated  portions  of 
benzol,  but  with  no  better  success.  Adopting, 
however,  the  micro  chemical  method,  allowing 
the  caustic  alkali  to  run  under  a  cover  glass  on 
the  slide  of  moistened  araroba,  whilst  under  the 
microscope,  and  by  this  means  dissolving  away 
gradually  the  soluble  portion  of  the  powder,  fragments  of  those  cells 
just  referred  to  as  composing  the  several  tissues  were  found  and  identi- 
fied without  difficulty. 
In  this  manner  broken  portions  of  libriform  cells  and  of  porous  ves- 
sels, also  of  cells  of  the  parenchyma  of  the  wood  were  discovered. 
Those  of  the  medullary  rays  were  too  fragmentary  to  be  distinguished 
satisfactorily  ;  being  a  very  delicate  tissue  it  was  scarcely  expected 
otherwise.  In  no  single  instance  were  cork  cells  present,  or  any  of 
the  sclerogen  cells  before  referred  to  as  forming  part  of  the  bark  ; 
starch,  although  found  in  the  cells  of  the  parenchyma  of  the  bark,  has 
not  been  detected  in  any  sample  of  araroba  examined.  It  is  fair  to 
infer,  therefore,  that  the  bark  does  not  form  any  portion  of  the  araroba, 
although  in  some  samples  of  it  pieces  may  be  found  just  in  the  same 
manner  as  pieces  of  the  wood  ;  also  that  from  the  fragments  of  the 
cells  in  the  araroba,  which  were  obtained  by  the  process  just  mentioned, 
a  conclusion  may  be  arrived  at  that  the  whole  of  the  cell  tissue,  com- 
No.  3. 
