Am.  Jour.  Pharm. 
Jan.,  1880. 
Coto  Barks. 
21 
astringent.  The  outer  layer  breaks  granular  and  nearly  even,  but  the 
inner  bark  has  a  coarsely  fibrous  and  splintery  fracture. 
Hartz  observed  that  the  membranes  of  all  the  cells,  except  those  of 
the  sclerenchyma  and  liber  are  tinged  blue  by  iodated  zinc  chloride,  as 
well  as  by  iodine  and  sulphuric  acid,  and  therefore  consist  of  pure 
cellulose.  The  sclerenchyma  and  bast  cells  are  of  a  golden-yellow 
color  and  are  not  tinged  by  immersion  in  solution  of  iodine  or  rosanilin, 
and  subsequent  washing  with  glycerin  ;  their  walls  consist  of  numerous 
concentric  layers,  which  contain  numerous  pores,  are  woody  and  very 
hard.  The  outer  and  inner  bark  contain  in  the  unthickened  parenchyma 
cells  a  little  tannin,  reacting  green  with  iron  salts,  phlobaphen-like 
substances,  which  are  soluble  in  alkalies,  a  small  quantity  of  little 
starch  granules,  and  drops  or  globules  composed  of  resin  and  volatile 
oils. 
Paracoto  bark  is  met  with  in  pieces  sometimes  0"j  meter  long,  40 
to  70  millimeters  wide,  and  from  12  to  18  millimeters  thick.  The 
outer  surface  is  frequently  covered  with  the  whitish,  deeply  fissured, 
cork  5  otherwise  the  color  and  the  fracture  are  the  same  as  in  true  coto 
bark.  The  odor  is  much  fainter,  and  resembles  that  of  nutmeg  ;  the 
taste  is  slightly  acrid.  This  bark  is  at  present  much  more  common  in 
the  market  than  the  former.  In  its  medicinal  action  it  is  decidedly 
weaker. 
The  investigation  of  the  chemical  constituents  gave  the  following 
results  : 
CoTOiN. — The  etherial  tincture  of  true  coto  bark  is  contentrated, 
and  while  still  warm,  mixed  with  warm  petroleum  benzin  ;  on  cooling 
a  considerable  quantity  of  a  blackish-brown  oleoresin  is  deposited,  and 
the  clear  solution,  left  to  spontaneous  evaporation  of  the  ether,  separates 
large  sulphur-yellow  crystals  of  cotoin.  The  oleoresin  is  boiled  with 
water  and  a  little  lime,  the  clear  brown-yellow  solution,  while  still  hot, 
is  supersaturated  with  acetic  or  hydrochloric  acid,  and  the  turbid  liquid 
^et  aside  for  about  twenty-four  hours,  when  the  cotoin  will  have  crys- 
tallized in  large  shining  yellowish  crystalline  plates,  and  upon  these  in 
-single  needles  or  in  acicular  groups.  The  crystals  are  purified  by 
recrystallization  from  boiling  water  with  the  addition  of  a  little  animal 
charcoal.  This  operation  is  very  tedious,  owing  to  the  cotoin  melting 
and  its  sparing  solubility  in  this  condition. 
Thus  prepared  cotoin  forms  pale-yellow,  usually  curved  prisms,  but 
