542  Method  for  Estimation  of  Pepsin.  {^^mb^itlT' 
offered  in  the  present  paper  sustaining  this  proposition  and  a  correc- 
tion is  made. 
Rose's  complete  method  follows : 
0.25  gram  globulin  of  the  pea  prepared  as  described  ...  is  dissolved 
in  100  Cc.  of  10  per  cent,  sodium  chloride  (by  warming  slightly  if  necessary) 
and  filtered.  Portions  of  the  clear  filtrate  of  1  Cc.  each  are  introduced  into  a 
series  of  11  small  test  tubes  about  1  cm,  in  diameter.  To  each  tube  is  added 
1  Cc.  of  0.6  per  cent,  hydrochloric  acid,  and  about  five  minutes  are  allowed  for 
the  development  of  the  turbidity.  A  measured  volume  of  the  stomach  con- 
tents is  then  exactly  neutralized  to  litmus  paper  with  dilute  alkali.  If  a  precipi- 
tate of  acid  protein  forms,  this  is  filtered  off,  and  the  clear  neutral  solution  is 
diluted  a  known  number  of  times  (usually  five)  with  distilled  water,  allow- 
ance being  made  for  the  dilution  of  neutralization.  A  portion  of  the  diluted 
juice  is  boiled,  and  amounts  decreasing  by  0.1  Cc.  added  to  the  tubes  of  turbid 
protein ;  to  the  first,  1.0  Cc. ;  to  the  second,  0.9  Cc. ;  to  the  third,  0.8  Cc. ;  and 
so  on  to  the  eleventh,  to  which  none  is  added.  The  unboiled  juice  is  then 
rapidly  added  in  increasing  amounts,  as  follows  :  To  the  first,  none ;  to  the 
second,  0.1  Cc. ;  to  the  third,  0.2  Cc. ;  to  the  fourth,  0.3  Cc. ;  to  the  fifth,  0.4  Cc. ; 
to  the  sixth,  0.5  Cc. ;  to  the  seventh,  0.6  Cc. ;  to  the  eighth,  0.7  Cc. ;  to  the  ninth, 
0  8  Cc. ;  to  the  tenth,  0.9  Cc. ;  and  to  the  eleventh,  1.0  Cc-  Each  of  the  tubes 
thus  has  a  total  volume  of  3.0  Cc. ;  and  a  total  acidity  of  0.2  per  cent,  of 
hydrochloric  acid. 
The  measurements  of  the  solutions  may  be  easily  and  accurately  made 
with  a  pipette  of  1  Cc.  capacity,  graduated  to  0.01  Cc.  The  tubes  are  well  shaken 
and  allowed  to  stand  in  a  thermostat  or  water  bath  for  15  minutes  at  a  tem- 
perature of  500  to  520  C.  Exactly  the  same  endpoint  is  obtained  by  keeping  the 
tubes  at  a  temperature  of  350  to  360  C.  for  one  hour.  At  the  end  of  the 
digestion  time  that  tube  in  the  series  is  selected  which  contains  the  least  amount 
of  gastric  juice  and  which  exhibits  no  turbidity.  The  peptic  activity  is  cal- 
culated on  the  basis  of  the  amount  of  gastric  juice  in  this  tube.  The  enzyme 
content  is  expressed  by  the  number  of  cubic  centimeters  of  the  0.25  per  cent, 
globulin  that  would  be  digested  by  1  Cc.  of  the  undiluted  gastric  juice  under 
examination,  if  the  activity  were  exerted  for  a  period  of  one  hour  at  350  to  360 
C,  or  for  15  minutes  at  50°  to  520  C.  For  example,  if  0:5  Cc.  of  a  gastric  juice 
diluted  five  times  clears  up  1  cubic  centimeter  of  the  0.25  per  cent,  globulin 
solution  in  15  minutes  at  the  given  temperature,  the  activity  of  the  solution 
would  be  expressed : 
Peptic  activity  =  (1  -^0.5)  X  5  =io. 
For  clinical  purposes  it  suffices  to  use  the  scale  of  pepsin  units  here  pro- 
posed, which  gives  figures  about  one-tenth  of  those  expressed  on  the  Jacoby- 
Solms  scale. 
Rose  further  states : 
In  the  above  method  the  conditions  are  constant  in  every  trial,  in  respect  to 
acidity,  volume,  protein  content,  and  temperature. 
This  statement  is  true  enough,  but  in  attaining  this  point  it  is 
