548  Method  for  Estimation  of  Pepsin.  (ADeceiXrPi9iT' 
with  toluene,  it  can  be  kept  for  a  month  or  more.  On  the  assump- 
tion that  exact  neutralization  only  inactivated  the  pepsin,  and  that 
it  might  be  reactivated  at  once,  though  this  is  not  possible  according 
to  Tichomirow,5  the  following  experiment  was  tried :  Some 
gastric  juice  was  neutralized  exactly  to  litmus  with  N/14  sodium 
hydroxide  and  at  once  the  previously  determined  acidity  was  attained 
by  adding  N/14  hydrochloric  acid.  This  juice  was  then  subjected 
to  the  determination  and  no  quantitative  amount  of  pepsin  found, 
while  with  the  unneutralized  juice  there  was  a  peptic  value  of  40. 
The  pepsin  can  be  determined  in  25  minutes  from  the  time  the  gastric 
contents  are  received,  provided  there  are  on  hand  stock  solutions  of 
pea  globulin  and  0.6  per  cent,  hydrochloric  acid.  Using  a  burette  to 
deliver  the  globulin  solution,  the  0.6  per  cent,  hydrochloric  acid,  and 
the  water,  and  graduated  pipettes  for  the  diluted  juice,  six  determina- 
tions can  be  completed  easily  in  an  hour  and  a  half. 
The  present  method  is  recommended  because  it  is  believed  to  be 
as  accurate  as  any  and  less  time  consuming.  That  it  will  check 
itself  is  shown  by  the  following  analyses  on  the  same  normal  indi- 
vidual on  different  days : 
Total 
acidity. 
Free 
acidity. 
Pepsin 
number. 
Contents 
removed 
after — 
Minutes. 
6l 
46 
25 
30 
46 
21 
31 
45 
6l 
44 
41 
60 
55 
42 
41 
60 
7i 
49 
41 
60 
89 
70 
40 
60 
83 
67 
41 
75 
84 
69 
41 
90 
The  low  value  .(25)  found  above  I  believe  is  due  to  the  fact  that 
only  30  minutes  elapsed  after  the  giving  of  the  test  meal,  as  Hawk  6 
and  his  collaborators  have  found  that  the  height  of  acid  and  pepsin 
secretion  is  not  reached  in  that  time.  The  high  value  (50)  found 
(see  Table  I)  in  a  normal  individual  may  be  due  to  a  hypersecretion 
of  pepsin,  called  forth  by  the  high  acidity  (90).  On  the  following 
day  the  same  case  with  a  total  acidity  of  60  showed  a  peptic  value 
of  41.  The  limit  for  normal  individuals  found  so  far  extends  be- 
tween 25  and  50.  The  following  table  gives  a  comparison  of  the 
results  obtained  on  the  same  contents,  by  the  proposed  method  and 
by  that  of  Jacoby  : 
