26  Acids  of  Gastric  and  Intestinal  Juices.  {Am-/^imarm^ 
brane  of  the  empty  stomach.  Before  weaning,  tartaric  acid  is  the  chief 
acid  found.  Since  tartaric  acid  has  been  found  to  be  the  acid  secreted 
by  all  carnivora,  recourse  must  be  had  to  the  pig,  which  in  its  dental 
and  digestive  system  corresponds  with  man,  in  future  experiments. 
In  dyspeptic  men,  a  quarter  of  an  hour  after  eating,  tartaric  acid 
and  hippuric  acid  were  found  together.  It  may  be  conjectured  that 
in  grave  diseases  of  the  stomach  hippuric  acid  may  be  entirely  replaced 
by  tartaric. 
In  all  the  cases  examined  in  healthy  or  sick  men,  and  also  in  ani- 
mals, no  lactic  or  sarcolactic  acid  was  found. 
The  hippuric  acid  of  the  gastric  juice  possesses  all  the  properties  of 
that  extracted  from  the  urine  of  herbivora  in  crystallization,  physical 
aspect,  and  reduction  to  benzene  by  dry  distillation  with  caustic  potash, 
mixed  or  not  with  quick  lime.  But  the  tartaric  acid  of  the  gastric 
juice  differs  from  the  vegetable  acid  in  some  of  its  properties,  especi- 
ally in  that  it  is  attacked  and  decomposed  in  the  cold  by  concentrated 
sulphuric  acid. 
The  reactions  of  dialyzed  gastric  juice  on  coloring  matters  differ 
very  much  from  those  of  hydrochloric  acid.  On  the  contrary,  they 
resemble  either  those  produced  by  hippuric  acid  or  tartaric  acid.  The 
yellow  color  of  Uffelmann's  reagent,  which  has  been  attributed  exclu- 
sively to  lactic  acid,  may  be  just  as  well  due  to  tartaric  or  hippuric 
acid,  and  is  not  characteristic,  therefore,  of  the  former. 
When  a  dilute  solution  of  hydrochloric  acid  is  added  to  Gunzburg's 
reagent,  and  it  is  heated,  a  red  color  appears,  at  a  temperature  of  75° 
to  78°.  A  similar  color  is  produced  by  hippuric  acid,  but  at  a  tem- 
perature of  105°  to  108°.  It  is,  therefore,  incorrect  to  assert  that 
only  inorganic  acids  produce  the  red  color,  and  that  Gunzburg's  solu- 
tion is  the  reagent  for  hydrochloric  acid.  When  normal  gastric  juice 
is  used  it  is  not  at  75°  that  the  red  coloration  appears,  as  would  be 
the  case  if  it  contained  hydrochloric  acid,  but  the  temperature  must 
be  raised  to  105°,  precisely  that  at  which  it  is  acted  on  by  hippuric 
acid. 
The  intestinal  juice  is  acid  in  the  whole  extent  of  the  small  intes- 
tine during  the  period  of  intestinal  digestion.  The  principle  which 
acidifies  it  is  none  other  than  the  same  tartaric  acid  which  is  secreted 
by  the  mucous  membrane  of  the  empty  stomach,  in  young  animals  dur- 
ing lactation,  and  in  adult  carnivora  during  digestion. 
Jas.  McNaught. 
