4  The  Fruit  of  Opuntia  Vulgaris.         { Am jaSui88P4barm' 
visible  through  the  thin  portion  of  the  testa  and  gives  that  part  of  the 
seed  a  bluish  black  appearance.  The  embryo  is  imbedded  in  the  oily 
albumen  and  has  the  cotyledous  set  contrary  to  the  sides  of  the  seed. 
It  forms  a  little  more  than  a  complete  circle  and  encloses  a  white, 
starchy  centre.  The  fruit  has  an  agreeable,  slightly  acid  and  very 
mucilaginous  taste  and  a  refreshing  odor.  It  is  frequently  eaten,  the 
seeds  of  necessity  swallowed  whole  as  it  would  be  almost  impossible  to 
crush  their  shell-like  testa  between  the  teeth,  or  to  separate  them  from 
their  mucilaginous  envelope. 
The  ripe  fruit  contains  68*2  per  cent,  of  moisture.  The  ash  amounted 
to  1*76  per  cent,  of  the  entire  fresh  fruit.  It  consists  largely  of  silica, 
besides  carbonates,  chlorides,  sulphates  and  phosphates,  with  potassium, 
sodium,  aluminium,  iron,  magnesium  and  calcium.  The  seeds  are 
about  one-sixth  the  weight  of  the  entire  fruit. 
The  seeds  and  enveloping  pulp  were  placed  in  a  coarse  linen  bag  to 
remove  the  mucilaginous  matter  by  maceration  in  water.  The  mucilage 
had  an  acid  reaction  and  possessed  a  beautiful  light  crimson  color 
which  was  completely  discharged  by  heating  on  a  water-bath  or  by 
the  addition  of  an  alkali. 
The  mucilage  was  not  affected  by  oxalate  of  ammonium  or  concen- 
trated solutions  of  ferric  chloride  or  of  sodium  borate,  but  a  precipi- 
tate was  formed  with  both  the  normal  and  the  basic  lead  acetate.  The 
mucilage  was  precipitated  by  alcohol,  obtained  on  a  filter,  dried  in 
scales  over  a  water-bath  and  preserved  for  further  examination.  The 
filtrate  from  the  mucilage  responded  clearly  to  tests  for  glucose  and 
pectous  compounds  but  contained  no  tannin.  The  skins  with  a  portion 
of  the  pulp  left  after  the  removal  of  the  seed,  were  macerated  in  alcohol 
for  several  days  the  filtered  product  being  a  wine-red  tincture  of  a 
pleasant  fruit-like  odor  and  acid  reaction  to  litmus.  This  tincture  was 
diluted  with  water  and  the  alcohol  distilled  off  on  a  water-bath.  In 
this  operation  the  wine-red  color  was  discharged,  the  liquid  assuming 
a  green  and  then  a  light  straw  color.  After  removing  the  coloring- 
matter  from  the  solution  with  benzin,  a  portion  was  precipitated  by 
lead  acetate.  The  precipitate  did  not  behave  as  lead  malate  when 
heated  under  water,  but  was  mostly  soluble  in  solution  of  ammonium 
chloride.  Another  portion  of  the  solution  gave  no  precipitate  with 
calcium  sulphate,  but  with  an  excess  of  calcium  hydrate,  a  white  pre- 
cipitate was  produced.  This  precipitate  was  soluble  in  a  solution  of 
potassium  hydrate,  and  the  solution  formed  a  gelatinous  precipitate  on 
