326 
The  Chemistry  of  the  Liver. 
Am.  Jour.  Pharm. 
June,  1892. 
the  bile-pigment  derivative  in  faeces.  Bile  pigment  differs  from 
blood  pigment  in  that  it  contains  no  iron ;  consequently,  iron  salts 
are  found  deposited  in  liver  tissue.  Small  quantities  of  phosphate 
of  iron  are  present  in  bile,  but  not  in  bile  pigment. 
The  work  of  the  bile  is  to  assist  in  the  digestion  of  fat,  which  it 
does  by  acting  both  as  an  emulsifying  and  a  saponifying  agent ;  the 
emulsification  of  the  fat  is  favorable  to  its  digestion,  and  the 
saponification  is  favorable  to  its  diffusion  or  osmosis.  Bile  prepares 
the  contents  of  the  stomach,  as  they  are  passed  into  the  intestine, 
for  the  digestive  action  of  pancreatic  juice ;  this  it  does  by  neutral- 
izing the  hydrochloric  acid  of  the  gastric  contents,  and  so  putting 
an  end  to  the  action  of  pepsin.  It  also  promotes  the  digestion  of 
starch  and  stimulates  the  peristaltic  movements  of  the  intestines. 
Being  a  weak  antiseptic  bile  retards  the  putrefaction  of  food  in  the 
intestines  ;  hence  in  cases  of  obstructive  jaundice,  in  which  bile  is 
absent  from  the  intestines,  the  stools  are  more  offensive  than  usual 
to  smell. 
The  liver  is  a  source  whence  sugar  is  discharged  into  the  circu- 
lation, for  the  portal  venous  blood  contains  only  I  part  of  sugar 
per  1,000,  whereas  the  hepatic  venous  blood  contains  2  parts  of 
sugar  per  i,ooo,  and  considering  the  great  quantity  of  blood 
passing  through  the  liver,  this  means  that  a  large  amount  of  sugar 
is  being  daily  produced  by  the  liver  and  discharged  into  the  blood 
leaving  that  organ.  From  what  is  this  sugar  produced  ?  It  is 
produced  from  a  substance  named  glycogen,  which  is  manufactured 
by  and  stored  up  in  the  liver  cells. 
Glycogen  (C6H10O5)  is  a  member  of  the  carbohydrate  group,  and 
is  an  isomer  of  starch  and  dextrin.  The  production  of  sugar  in  the 
liver  takes  place  in  two  stages  ;  first,  the  formation  of  glycogen, 
and  second,  the  conversion  of  glycogen  into  sugar.  Glycogen  is 
derived  from  food,  and  especially  from  carbohydrate  foods.  It  is 
also  derived  from  proteids,  but  not  from  fat,  as  the  livers  of  animals 
fed  exclusively  on  fat  contain  no  glycogen.  If  minced  up  liver  is 
boiled  with  water  the  glycogen  is  extracted,  and  can  be  precipitated 
by  the  addition  of  alcohol  to  the  aqueous  extract.  It  is  a  white 
powder  soluble  in  water  and  yielding  an  opalescent  solution* 
Iodine  gives  a  mahogany  brown  color  with  glycogen  ;  by  boiling 
with  dilute  sulphuric  acid  glycogen  readily  combines  with  water 
and  yields  glucose. 
