Am.  Jour.  Pharm. 
Jane,  1892. 
The  Chemistry  of  the  Liver. 
325 
bulk,  make  into  a  paste  with  animal  charcoal,  dry  at  ioo°  C.  and 
extract  with  alcohol  ;  from  the  alcoholic  solution  the  bile  salts  may 
be  precipitated  by  adding  ether  in  excess.  Pettenkofer's  test  for 
the  bile  acids  consists  in  the  development  of  a  red  color  on  the 
addition  of  strong  sulphuric  acid  and  a  concentrated  solution  of 
cane  sugar.  The  two  bile  acids  may  be  separated  from  each  other 
by  dissolving  the  sodium  salts  of  the  two  bile  acids  in  water,  and 
adding  neutral  lead  acetate,  when  the  glycocholate  of  lead  is 
precipitated.  Filter,  and  add  to  the  filtrate  basic  lead  acetate  and 
ammonia,  when  the  taurocholate  of  lead  is  precipitated.  From  the 
lead  salts  the  bile  acids  can  be  liberated  by  means  of  sulphuretted 
hydrogen.  The  glycocholate  and  taurocholate  of  sodium  are  found 
very  sparingly  in  the  faeces,  and  are  only  represented  to  a  slight 
extent  in  the  urine.  It  is  calculated  that  about  seven-eighths  of 
these  bile  salts  are  re-absorbed  from  the  intestines  and  returned  to 
the  liver,  in  the  form  of  the  simpler  constituents,  glycocine,  taurine 
and  cholalic  acid,  into  which  they  have  split  up  in  the  intestines, 
these  bodies  being  again  united  within  the  liver  to  form  the  bile 
salts.  If,  therefore,  the  liver  normally  depends  upon  the  recovery 
from  the  intestines  of  so  large  a  proportion  of  its  bile  salts,  is  it  to 
be  wondered  at  that  the  liver  becomes  so  quickly  deranged,  as  it 
does  during  an  attack  of  profuse  diarrhoea,  when  the  bile  salts 
which  should  be  returned  to  the  liver  are  swept  away  in  the  stools  ? 
Cholesterin  (C26H44Oj. — The  chief  interest  of  this  constituent  of 
the  bile  lies  in  the  fact  that  it  forms  the  main  constituent  of  the 
concretions  known  as  gall  stones.  Very  little  is  known  as  to  its 
mode  of  formation  ;  in  a  gall  stone  its  presence  can  be  detected  by 
crushing  the  stone,  dissolving  out  the  cholesterin  with  chloroform, 
and  adding  strong  sulphuric  acid  to  the  chloroform  solution,  when 
a  red  color  is  produced. 
The  yellow  coloring  matter  of  the  bile  of  man  and  of  the  car- 
nivora  is  due  to  a  pigment  bilirubin  C32H36N406;  the  green  color- 
ing matter  of  the  bile  of  herbivora  is  due  to  a  pigment  biliverdin 
C32H36N408.  These  pigments  are  derived  from  blood-coloring 
matter,  for  bilirubin  is  indistinguishable  from  haematoidin,  a 
pigment  found  in  old  blood  deposits.  Biliverdin  is  a  more  highly 
oxidized  state  of  bilirubin ;  either  of  them  if  reduced  with  nascent 
hydrogen  yields  hydrobilirubin,  C32H36N405,  which  is  identical  with 
urobilin,  the  bile-pigment  derivative  in  urine,  and  with  stercobilin, 
