472  Relative  Value  of  Different  Pepsin  Tests.  {"^""sSt'if^s^"^' 
moist  filter  into  a  platinum  dish,  and  the  filter  carefully  washed.  The 
solution  is  again  evaporated  to  dryness  and  weighed.  The  peptone  is 
then  incinerated  with  ammonium  carbonate,  and  the  weight  of  the  ash 
deducted  leaves  the  weight  of  the  pure  peptone,  or  the  representative 
of  the  digestive  power  of  the  pepsin. 
The  good  qualities  of  the  above  test  are  the  following : 
1.  Simplicity. 
2.  No  guesswork,  troublesome  calculations  or  the  use  of  questionable 
factors. 
3.  No  weighing  of  albumen  dissolved  in  hydrochloric  acid,  undi- 
gested albumen  and  intermediary  products  along  with  the  peptone. 
This  is  all  obviated  by  the  use  of  soluble  egg  albumen,  coagulation 
and  filtration  or  removal  of  the  undigested  portion  as  detailed  above. 
4.  The  ease  with  which  it  is  possible  to  duplicate  and  still  obtain 
concordant  results. 
On  the  other  hand,  the  objections  to  this  process  are  the  follow- 
ing : 
1.  The  great  difficulty  of  procuring  absolutely  pure  soluble  dried 
egg  albumen.  This  source  of  error,  however,  in  my  opinion,  is  very 
slight,  because  in  each  test  a  large  excess  of  albumen  is  always  used, 
and  consequently  the  pepsin  always  has  enough  albumen  to  act  upon. 
Besides  this  it  must  be  remembered  that  only  the  peptone  formed  is 
weighed,  and  not  the  amount  of  undigested  albumen,  as  is  the  case 
with  the  U.  S.  P.  test. 
2.  It  may  be  objected  to  this  test  that  the  results  obtained  are 
expressed  by  the  weight  of  peptone  formed  and  not  by  the  weight 
of  albumen  dissolved,  and  consequently  the  figures,  being  based 
upon  dry  pe])tone,  will  be  much  lower  than  when  the  result  is 
expressed  as  so  much  moist  or  coagulated  albumen.  If  this,  how- 
ever, be  objected  to,  it  is  comparatively  easy  to  obtain  higher 
figures  by  a  simple  calculation.  Assuming  that  the  amount  of  dry 
peptone  obtained  is  equivalent  to  so  much  dry  albumen,  then  by 
multiplying  the  weight  of  the  latter  by  8  (Manwaring's  multiplier) 
we  would  obtain  the  equivalent  in  coagulated  or  moist  albumen.  I 
do  not  think  it  necessary  or  advisable  to  follow  this  course,  as  it  in- 
volves the  use  of  a  multiplier  which,  as  already  pointed  out,  is  ques- 
tionable. 
3.  It  takes  a  little  longer  to  make  a  test  by  this  process,  but  if  ac- 
curacy is  thereby  gained  the  process  is  to  be  preferred. 
