464 
Pepsin. 
/Am.  Jour.  Pharm^ 
X      Sept.,  1888. 
pound.  A  second  base  has  also  been  observed  by  Paul  and  Cownley 
shortly  after  the  publication  of  their  paper,  Chemical  Notes  on  Tea/^ 
(Amer.  Jour.  Phar.,  1887,  p.  626) ;  the  acid  liquid  from  which  the 
theine  had  been  removed  by  chloroform,  was  rendered  alkaline  by 
potassa,  and  again  shaken  with  chloroform,  when  a  very  small  quan- 
tity of  alkaloid  was  obtained,  apparently  amorphous,  insoluble  in  hot 
water,  but  soluble  in  ether,  and  therefore  differing  from  both  theine 
and  theobromine  {Phar.  Jour,  and  Trans.,  July  14,  1888,  p.  24). — 
Editor  Am,  Jour.  Phar. 
PEPSIN. 
By  a.  Percy  Smith,  F.I.C.,  F.C.S.,  Rugby. 
The  method  usually  adopted  for  estimating  the  peptonising  power 
of  pepsina  porci  consists  in  dissolving  1  to  2  grains  in  8  to  12  ounces 
of  water,  to  which  40  to  60  minims  of  hydrochloric  acid  has  been 
added.  500  to  1000  grains  of  hard-boiled  white  of  egg,  granulated 
by  rubbing  through  a  wire  sieve,  is  immersed  in  the  liquid,  and  the 
whole  kept  at  98°  to  130°  F.  for  four  hours,  when  the  undissolved 
albumen  is  filtered  off  through  muslin,  and,  after  partial  drying,  i& 
weighed  to  ascertain  the  amount  dissolved.  The  variable  numbers 
above  quoted  embrace  various  formulae  recommended  by  different 
experimenters. 
This  method  of  analysis  is  excessively  crude  and  untrustworthy. 
When  hard-boiled  white  of  egg  is  kept  in  warm  water  it  absorbs  a 
considerable  quantity  of  that  menstruum,  as  much  as  several  units  per 
cent. ;  consequently,  on  weighing  the  residual  albumen,  you  may  find 
that  the  weight  is  greater,  instead  of  less  than  that  with  which  you 
started,  the  gain  in  Aveight  due  to  absorbed  water  more  than  counter- 
balancing the  loss  obtaining  through  solution,  as  has  happened  with 
indifferent  samples  of  pepsin.  Then  who  shall  say  when,  by  simple 
air  drying,  the  albumen  has  regained  its  former  condition?  The  enor- 
mous quantity  of  albumen  is  foreign  to  the  usual  habits  of  the  scientific 
analyst,  and  involves  an  enormous  waste  of  time  in  manipulation. 
One  trial  of  this  method  was  enough  for  me.  The  first  modification 
I  adopted  consisted  in  substituting  for  the  large  quantity  of  granulated 
albumen  a  single  half  of  the  white  of  an  egg  in  one  piece.  I  likewise 
arranged  a  check  experiment  in  which  the  pepsin  was  omitted,  other 
conditions  remaining  unaltered.   At  the  end  of  four  hours  the  residual 
