546 
Method  for  Estimation  of  Pepsin. 
{ 
Am.  Jour.  Pliarm. 
December,  1915. 
Unneutralized  juice. 
Neutralized  juice. 
Proposed 
method. 
Jacoby 
method. 
Rose 
method. 
Jacoby 
method. 
Remarks. 
41 
41 
41 
41 
IOO 
IOO 
IOO 
Trace. 
Trace. 
Trace. 
Trace. 
Trace.  + 
Trace.  + 
Trace. -j- 
Trace.  + 
Normal. 
Do. 
Do. 
Pellagra. 
The  following  method  has  been  adopted  in  this  laboratory.*  The 
gastric  contents  are  strained  through  cheesecloth.  Two  Cc.  are 
measured  by  means  of  an  Ostwald  pipette  into  a  25  Cc.  stoppered 
volumetric  cylinder,  and  diluted  to  the  mark  with  distilled  water. 
Into  each  of  seven  small  test  tubes  (1  X  10  cm0  is  measured,  with 
an  Ostwald  pipette,  1  Cc.  of  a  0.25  per  cent,  filtered  pea  globulin  in  10 
per  cent,  sodium  chloride  solution.  To  each  tube  is  added  1  Cc.  of 
0.6  per  cent,  hydrochloric  acid,  also  by  means  of  an  Ostwald  pipette. 
The  tubes  are  allowed  to  stand  about  5  minutes,  until  the  maximum 
turbidity  develops.  To  the  first  five,  distilled  water  is  added  as  fol- 
lows :  To  the  first,  0.9  Cc. ;  to  the  second,  0.8  Cc. ;  to  the  third,  0.7 
Cc. ;  to  the  fourth,  0.6  Cc. ;  and  to  the  fifth,  0.2  Cc. ;  to  the  sixth  and 
seventh,  none.  Then  there  are  rapidly  added  to  each  test  tube  the 
following  amounts  of  the  1/12.5  gastric  juice  ;  to  the  first,  0.1  Cc. ;  to 
the  second,  0.2  Cc. ;  to  the  third,  0.3  Cc. ;  to  the  fourth,  0.5  Cc. ; 
to  the  fifth,  0.8  Cc. ;  to  the  sixth,  1.0  Cc. ;  and  to  the  seventh,  1.0  Cc. 
of  the  diluted  juice  boiled.  These  measurements  can  be  accurately 
made  with  a  1  Cc.  pipette  graduated  in  0.01  Cc.  All  tubes  are  then 
immersed  for  15  minutes  in  a  water  bath  at  500  to  52 0  C.  At  the 
end  of  this  time,  the  tube  is  selected  which  is  clear  and  contains  the 
least  amount  of  diluted  gastric  juice.  Upon  this  basis,  the  peptic 
activity  is  calculated  as  the  number  of  Cc.  of  0.25  per  cent,  globulin 
digested  by  1  Cc.  of  undiluted  gastric  juice.  For  example,  if  tube 
2  containing  0.3  Cc.  of  a  12.5  times  diluted  juice  be  clear,  then  the 
result  would  be  expressed : 
Ordinarily  this  scheme  of  seven  tubes  is  used,  though  it  is  hot  a 
rule.  If  the  free  acidity  be  high,  sometimes  a  dilution  of  1/25  is 
made.  The  number  of  tubes  used  will  depend  upon  the  accuracy 
desired. 
Peptic  activity  =  (1  ~  0.3)  X  12.5  =  41.2. 
*  I  take  pleasure  in  here  thanking  Dr.  R.  C.  Lewis,  of  the  staff,  for  the 
preparation  of  pea  globulin  used  in  these  experiments. 
