322 
The  Chemistry  of  the  Liver, 
(Am.  Jour.  Pharm. 
1       June,  1892. 
from  which  they  separate.  They  are  usually  observed  to  be  sur- 
rounded by  a  lighter  colored,  or  even  quite  colorless,  layer,  the  col- 
oring matter  being  deposited  with  such  rapidity  upon  the  growing 
crystal  that  the  slow  diffusion  of  the  dye  from  the  more  distant  parts 
of  the  solution  is  not  sufficient  to  make  up  for  the  decreasing  con- 
centration in  the  neighborhood  of  the  crystal. 
The  coloring  of  the  crystals  is  in  nearly  all  cases  dichroic,  a  proof 
that  the  coloring  matter  actually  enters  in  some  way  into  the  struc- 
ture of  the  crystal.  The  remarkable  rule  is  observed  that  only  one 
of  the  two  rays  produced  by  double  refraction  is  colored,  whilst  the 
other  appears  to  be  perfectly  white,  the  colorless  ray  being  always 
the  one  which  has  undergone  the  least  refraction. 
If  two  coloring  matters  are  present,  in  the  solution,  the  presence 
of  the  one  often  hinders  the  absorption  of  the  other.  In  some  cases, 
however,  the  reverse  takes  place,  and  a  coloring  matter  which  alone 
wouid  not  be  absorbed  may  become  so  when  some  second  coloring 
matter  is  added.  Change  of  the  solvent,  or  the  addition  of  other 
solid  or  liquid  foreign  matter,  may  act  in  a  similar  manner. 
Different  crystals  are  only  capable  of  taking  up  certain  organic 
dyes,  so  that  two  compounds  of  perfectly  similar  appearance  may 
be  capable  of  combining  the  one  only  with  one,  and  the  second 
only  with  some  other  dye.  This  fact  may  obviously  be  made  avail- 
able in  distinguishing  crystals  one  from  another.  It  may  also, 
perhaps,  be  applicable  for  the  purification  of  certain  dye-stuffs. 
THE  CHEMISTRY  OF  THE  LIVER.1 
By  A.  P.  Luff,  M  D.,  B.Sc,  M.R.C.S. 
Although  I  shall  trouble  you  with  as  few  anatomical  and 
physiological  details  as  possible,  yet  it  is  necessary  for  the  com- 
prehension of  the  subject  that  I  should  give  you  some  idea  as  to 
the  relationship  of  the  liver  to  the  alimentary  canal  and  to  the 
circulation  in  general.  The  liver  is  a  large  gland  connected  by 
means  of  the  bile-duct  with  the  upper  part  of  the  intestinal  tract ; 
it  is  composed  of  a  number  of  small  lobules,  each  of  which  may  be 
regarded  as  a  miniature  liver,  since  the  chemical  changes  occurring 
in  the  liver  are  the  sum  of  the  chemical  changes  occurring  in  the 
1  Read  before  the  Chemists'  Assistants'  Association  ;  reprinted  from  Phar. 
Jour,  and  Transactions,  April  23,  1892,  p.  884. 
