The  Testing  of  Pepsin, 
Am.  Jour.  Pharm. 
Mar.,  1880. 
acids,  acetic  and  butyric.  The  utility  will  hence  be  understood  of 
employing  in  such  a  case  alkalies,  which  in  saturating  the  free  acids 
induce  a  fresh  secretion  of  hydrochloric  acid  and  thus  restore  to  the 
gastric  juice  all  its  digestive  power.  It  will  be  understood  also  that  to 
attain  the  same  object  sometimes  solutions  of  hydrochloric  acid  and 
sometimes  of  the  alkaline  bicarbonates  have  been  given  with  success. 
It  is  necessary,  besides,  in  this  case,  that  the  acetates  and  butyrates 
should  be  eliminated  by  stomachal  absorption  ;  otherwise  they  would  be 
decomposed  and  the  inactive  acids  again  set  free  by  the  hydrochloric 
acid  secreted  normally  or  administered  as  medicine. 
To  return  to  the  testing  of  pepsin  by  coagulated  white  of  egg,  one 
objection  that  may  be  brought  against  it  is  that  it  does  not  establish  a 
sufficient  gradation  in  the  transformations.  However  this  may  be,  the 
method  of  operating  is  a  follows  : 
An  egg  is  kept  in  boiling  water  during  half  an  hour,  and  the  very 
coherent  white  is  then  passed  through  a  moderately  fine  strainer.  5 
grams  of  this  coagulated  albumen,  put  into  contact  at  40°C.  with  25 
grams  of  hydrochloric  acid  containing  1-50  of  HCl  per  liter,  ought  to 
be  dissolved  in  four  to  five  hours  by  O'lO  gram  of  pepsin  of  good 
quality.     It  is  necessary  to  agitate  the  flask  every  half  hour. 
Test  by  Fibrin. — This  appears  to  me  to  present  great  advantages  over 
the  preceding.  The  phenomena  are  very  distinct  and  very  comparable. 
Whatever  may  be  the  origin  of  a  ferment,  in  the  same  conditions  of 
time,  temperature  and  acidity  of  the  menstruum,  its  exact  equivalence 
can  be  determined  by  relation  to  other  specimens.  The  following  are 
the  conclusions  I  have  arrived  at  with  respect  to  the  best  conditions  for 
the  transformation  of  fibrin. 
The  temperature  of  50°C.  is  that  of  the  maximum.  The  same  pepsin 
is  about  four  times  less  active  at  40°  than  at  fO^C. 
The  acid  most  favorable  to  the  transformation  is  hydrochloric  acid. 
In  order  to  approach  the  action  of  this  acid  it  is  necessary  to  employ 
relatively  large  quantities  of  lactic  or  tartaric  acids,  about  25  to  30 
grams  per  liter.  With  lactic  acid  in  the  proportion  of  20  grams  per 
liter  the  action  is  five  times  less  than  that  which  corresponds  to  a  3  per 
1,000  solution  of  hydrochloric  acid.  With  hydrochloric  acid  the  most 
favorable  action  is  obtained  with  a  solution  containing  between  2  and  5 
grams  of  real  HCl  per  liter. 
To  recapitulate,  it  appears  that  the  acidity  of  the  gastric  juice  does 
not  exceed  2  to  3  grams  per  liter  of  acid  expressed  as  HCl,  which 
