AFrtr7*ry.imm'}     Analysis  of  the  Gastric  Contents.  95 
The  best  test  for  lactic  acid  for  practical  work  is  the  ferric-chloride 
test.  A  colorless  solution  of  neutral  ferric  chloride  is  turned  a 
lemon-yellow  (gelbgrun)  color  by  lactic  acid.  A  more  striking 
application  of  the  test  is  seen  in  the  Uffleman  lactic  acid  test.62 
Uffleman's  solution  consists  of  10  c.c.  of  4  per  cent,  carbolic  acid, 
20  c.c.  of  water  and  one  drop  of  10  per  cent,  neutral  ferric  chloride. 
The  pale  amethyst  color  of  this  solution  is  bleached  and  replaced 
by  a  lemon-yellow  color  by  the  addition  of  lactic  acid. 
This  ferric-chloride  test  responds  to  the  presence  of  y2  gramme 
per  mille  lactic  acid.  As  the  amount  of  lactic  acid  contained  in  the 
Ewald  test  breakfast  is  at  most  gramme  per  mille,  this  test  can 
be  used  as  an  index  of  the  presence  of  produced  lactic  acid  after 
the  ingestion  of  this  meal.61, 63 
In  testing  for  lactic  acid  in  the  gastric  contents  this  ferric-chloride 
test  must  be  used  in  a  modified  form,  since  the  straight  test  or  Uffle- 
man modification  are  interfered  with  by  certain  substances  which 
may  be  present  in  the  normal  or  pathological  contents.61-64 
Thus  glucose,  alcohol,  peptones,  carbonates,  bile,  butyric  acid, 
potassic  sulpho-cyanide,  all  substances  which  may  be  present  in  the 
gastric  contents,  may,  to  a  greater  or  less  degree,  simulate  the  test.61 
Phosphates,  hydrochloric  acid  and  fatty  acids,  if  in  sufficient 
amount,61  inhibit  the  test.  These  substances  must,  therefore,  be 
excluded  before  making  the  test  for  lactic  acid  in  the  contents.  A 
most  satisfactory  method  of  excluding  these  substances  and  testing 
for  lactic  acid  in  the  gastric  contents  is  the  De  Jong  method.65 
To  5  c.c.  of  the  gastric  contents  add  two  drops  of  strong  hydro- 
chloric acid  ;  heat  the  mixture  to  a  syrupy  consistency  over  a  flame 
or  water-bath  ;  shake  the  residue  with  10  c.c.  of  ether ;  separate 
the  ether ;  to  this  ethereal  extract  add  5  c.c.  of  water  and  one  drop 
of  5  per  cent,  neutral  ferric  chloride.  If  lactic  acid  be  present  in 
amount  over  y2  gramme  per  mille,  a  lemon- yellow  color  will  be 
obtained.66 
61  De  Jong:  Archiv.f.  Verdauungskrankheite?i,  Bd.  II,  H.  1  ;  also  Langguth, 
same  Archives,  Bd.  I,  s,  365. 
62  Uffleman:  Deutsches  Archiv.f.  klin.  Med.,  Bd.  XXVI,  s.  431. 
63  Lactic  acid  may  be  produced  in  the  normal  stomach  by  the  action  of  free 
HC1  upon  the  lactates  of  the  food,  but  it  is  not  built  up  there. 
64  Boas  \Deutsch.  med.   Woch.,  No.  39,  1893  ;  Berl.  klin.  Woch.,  No.  9,  1895. 
65  Dejong:  Archiv.f.  Verdauitngskrankheiten,  Bd.  II,  H.  1,  s.  59. 
6 6  This  is  the  best  method  for  clinical  work  yet  given.    The  other  reliable 
