470  Relative  Value  of  Different  Pepsin  Tests,  {^"^'^^^'.lim^'^' 
if  by  previously  weighing  bottle  and  contents  and  afterwards  making 
up  with  water  any  loss  from  evaporation,  the  quantity  of  albumen  dis- 
solved may  be  easily  determined  as  follows  : 
From  the  settled  contents  of  the  test  bottle  pipette  off  10  cc.  and 
evaporate  to  dryness — until  weight  is  constant — in  a  watch  glass. 
From  this  dry  residue  figure  as  follows  (1  pt.  of  peptone  or  intermediate 
products  representing  1  pt.  of  original  albumen) : 
Suppose  10  cc.  of  the  liquid  =  0.2  gm.  dry  residue;  t!t  times  its 
weight  =  the  quantity  of  water  contained  in  the  10  cc.  that  Avas  de- 
rived from  the  albumen  dissolved  ;  10  cc.  of  liquid  less  1.4  cc.  of 
water  leaves  8.6  cc.  water  taken  from  the  154  cc.  of  acidulated  water 
in  making  the  test. 
1.6  grms.  or  8  times  0.2  grm.  dry  residue  =  the  quantity  of  albu- 
men in  its  natural  state  as  originally  used,  that  has  been  dissolved  in 
the  10  cc.  of  liquid  evaporated  to  dryness. 
Therefore,  if  8.6  cc.  acidulated  water  holds  1.6  gm.  egg-albumen, 
then  154  cc.       "  "  28.5 
Then,  as  0.015  gm.  pepsin  dissolved  28.5  gms.  coagulated  egg- 
albumen,  1  pt.  would  dissolve  1900  times  its  weight. 
The  use  of  the  multiplier  7  and  8  is  based  on  the  fact  that  egg- 
albumen  averages  12 J  per  cent,  or  J-  dry. 
As  will  be  seen,  this  test  is  quite  a  departure  from  the  U.  S.  P. 
test,  and  in  some  respects  is  an  improvement  upon  the  latter,  but  I 
object  to  it  on  several  points,  viz. : 
1.  It  makes  no  provision  for  other  than  concentrated,  or,  as  Man- 
waring  calls  them,  pure  pepsins,  while  in  reality  the  number  of  these 
is  small  compared  to  the  saccharated  pepsins. 
2.  The  peptic  principle  is  not  killed  at  145°  F.  =  62.2°  C;  but 
digestion  may  and  does  continue  up  to  80°  C. 
3.  Of  the  undigested  albumen  remaining  in  the  test  bottle,  a  little 
remains  suspended  in  the  liquid,  is  pipetted  off  and  adds  to  the  weight 
of  the  dry  residue. 
4.  On  evaporating  the  10  cc.  to  dryness  the  residue  chars  owing  to 
the  free  H  CI  present. 
5.  The  residue,  not  charred,  is  a  mixture  of  undigested  albumen, 
partly  digested  albumen  and  fully  digested  albumen  or  peptone. 
Peptone  only  being  assimilable  in  the  human  system — not  the  interme- 
diary products — the  amount  of  true  peptone  formed  indicates  the 
strength  of  the  pepsin. 
