Am.  Jour.  Pharm. 
Mar.,  1880. 
The  Testing  of  Pepsin. 
155 
THE  TESTING  OF  PEPSIN. 
By  a.  Petit. 
Recent  investigation  having  directed  attention  to  the  ferments  which 
preside  over  the  transformation  of  the  various  alimentary  matters,  it 
appeared  to  me  that  it  would  be  useful  to  define  the  present  state  of 
this  interesting  question,  and  particularly  to  state  the  method  of  testing: 
most  convenient  to  be  adopted  for  these  ferments,  of  which  the  medi- 
cal employment  is  becoming  more  and  more  common. 
In  commencing  this  study  I  would  recall  that  all  the  facts  relative  t» 
the  action  of  pepsin  and  diastase  have  been  explained  with  the  greatest 
clearness  by  M.  Mialhe.  Upon  reperusing  the  memoirs  of  1845  and 
1 846  it  will  be  seen  that  his  opinions,  sharplv  discussed  at  the  time  when 
they  appeared,  are  now  accepted  by  all  investigators  occupied  with  the- 
phenomena  of  digestion.  On  the  present  occasion  I  will  deal  only 
with  certain  facts  connected  with  the  transformation  of  nitrogenous 
foods  by  pepsin. 
These  substances-^albumen,  fibrin,  casein,  etc. — ^submitted  to  the 
combined  action  of  pepsin  and  an  acid,  are  transformed  at  first  into  a 
compound,  named  caseiform  albumen  by  M.  Mialhe,  and  more  recently 
syntonin  ;  then  into  another  substance — the  ultimate  product  of  the 
stomachic  digestion  of  albuminoid  matters — the  albuminose  of  Mialhe,, 
or  the  peptone  of  Lehmann.  According  to  their  source,  these  peptones^ 
although  they  are  very  probably  isomers,  differ  from  one  another  by 
their  action  upon  polarized  light. 
M.  Henninger  thinks  that  the  peptones  are  formed  by  the  hydration 
of  albuminoid  matters,  and  as  they  combine  indifferently  with  acids 
and  bases  he  considers  them  as  weak  acid  amides.  M.  Meissner  divided 
the  products  of  transformation  of  albuminoid  matters  into  parapeptones,, 
metapeptones,  dyspeptones  and  peptones  «,  ^  and  y  ;  but  these  divi- 
sions can  no  longer  be  accepted  in  the  present  state  of  science. 
The  essential  characters  of  peptones  are  those  of  not  being  precipi- 
tated by  saturation  of  the  acid  liquids  holding  them  in  solution,  or  by 
nitric  acid,  or  by  ferrocyanide  of  potassium  added  to  acetic  acid.  They 
are  mostly  soluble  in  water,  even  after  having  been  precipitated  from 
their  aqueous  solution  by  excess  of  alcohol. 
The  test  by  nitric  acid  has  a  prime  importance,  as  will  appear  sub- 
sequently. It  permits,  in  fact,  of  ascertaining  rapidly  whether  the 
transformation  is  more  or  less  advanced.  When  nitric  acid,  added  drop 
