Am.  Jour.  Pharrn.  \ 
June,  1S92.  J 
The  Chemistry  of  the  Liver. 
327 
The  amount  of  sugar  in  the  venous  blood  of  muscle  is  below 
that  present  in  the  arterial  blood  ;  sugar  is  therefore  consumed  by 
living  muscle,  to  which  it  is  a  food  and  heat  producing  substance. 
Glycogen  must  therefore  be  regarded  as  a  temporary  carbohydrate 
reserve,  stored  up  for  the  time  in  the  liver  and  capable  of  conversion 
into  sugar,  as  demand  for  the  latter  arises  within  the  system.  On 
the  one  hand,  it  is  formed  by  and  deposited  in  the  liver  cells  from 
materials  brought  to  the  liver  in  the  portal  blood  ;  on  the  other 
hand,  it  is  given  out  by  the  same  cells  in  the  form  of  sugar,  as 
necessity  arises.  The  glycogen  of  the  liver  is  diminished  by  fasting, 
by  fevers,  and  in  cases  of  poisoning  by  arsenic  and  phosphorus,  the 
diminution  in  the  last  three  cases  being  due  to  derangement  of 
function  of  the  liver  cells.  The  glycogenic  function  of  the  liver  is 
intimately  associated  with  the  interesting  disease  known  as  diabetes. 
In  this  disease  there  is  an  excess  of  sugar  in  the  blood,  which  excess 
is  disposed  of  by  the  kidneys,  and  so  appears  in  the  urine.  This 
excess  of  sugar  in  the  blood  may  be  attributed  to  abnormal  action 
of  the  liver,  i.  e.,  increased  production  of  sugar,  or  to  deficient 
consumption  of  sugar  by  the  tissues.  It  is  probable  that  both 
causes  co-operate  in  the  causation  of  diabetes,  although  the  former 
is  doubtless  the  more  potent  factor.  Since  the  system  can  only 
dispose  of  a  definite  quantity  of  sugar  in  a  certain  time,  if  the  blood 
contains  more  sugar  than  usual,  the  excess  of  sugar  must  of  necessity 
make  its  appearance  in  the  urine.  It  follows  that  it  is  essential  in 
the  treatment  of  diabetic  patients  to  exclude  from  their  diet  all 
starchy  and  saccharine  substances. 
Nitrogen  enters  the  organism  in  the  different  proteid  articles  of 
food ;  it  leaves  mainly  as  urea.  The  liver  is  the  chief  place  where 
urea  is  formed,  the  kidneys  acting  as  filters  through  which  it  passes 
in  solution.  As  to  the  actual  formation  of  urea  and  uric  acid 
in  the  liver  not  much  is  known.  We  are  acquainted  with  some 
intermediate  substances  between  proteids  and  urea,  bodies  which 
are  less  complex  than  proteids,  but  which  are  more  complex  than 
urea  ;  these  substances  are  certainly  derived  from  proteids,  and  are 
probably  some  of  the  antecedents  of  urea.  They  are,  leucine  and 
tyrosine  in  the  intestines,  glycocine  in  glycocholic  acid  and  in  the 
intestines,  creatine  and  sarcosine  in  muscle,  and  uric  and  hippuric 
acids  in  urine. 
It  is  known  that  the  introduction  of  glycocine  and  leucine  into 
