Am.  Jour.  Pharm.l 
March,  1893.  J 
Manufacture  of  Pepsin. 
145 
peptone  increases  with  the  length  of  time  during  which  digestion  is 
carried  on,  and  also  with  an  increase  of  temperature  during  the 
operation.  Next  morning  any  dust  or  film  on  the  surface  is 
carefully  removed,  and  the  clear  yellowish  green  solution  removed 
and  strained ;  if  not  perfectly  clear,  digestion  has  not  been  perfect, 
the  temperature  having  been  either  too  high  or  too  low,  and  the  liquid 
cannot  be  used  for  scaling.  When  clear  and  successful,  the  above 
quantities  should  yield  from  95  pounds  to  100  pounds  of  perfectly 
clear  liquid,  of  the  consistence  of  thin  syrup,  and  should  leave  about 
25  pounds  of  sediment.  The  clear  solution  is  either  evaported  in  vacuo, 
or  placed  in  shallow  trays,  and  further  evaporated  to  about  30  pounds 
of  syrupy  fluid,  at  a  temperature  not  higher  than  11 2°  F.  When 
thus  concentrated,  it  is  again  strained,  spread  upon  glass  plates,  and 
scaled  in  a  proper  scaling  room.  The  concentrated  pepsin  solution 
keeps  tolerably  well  for  about  two  days,  but  it  is  best  to  add  about 
one  ounce  of  chloroform  to  each  gallon  of  fluid.  An  experienced 
scaler,  with  a  good  scaling  room,  can  get  from  5  pounds  to  6  pounds 
of  good  scales  from  the  above  quantity. 
The  so-called  crystal  pepsin,  or  peptone  pepsin,  is  prepared  in 
exactly  the  same  way  as  the  scales,  except  that  instead  of  thin  scales 
being  formed,  the  concentrated  pepsin  solution  is  dried  in  thicker 
sheets,  like  fine  glue,  and  broken  up  when  dry  into  small  pieces. 
The  words  crystal  and  peptone,  applied  to  this  class  of  preparations, 
are  both  inappropriate,  since  they  are  neither  crystalline  nor  true 
peptones,  but  rather  mixtures  of  pepsin  and  syntonin,  with  a  little 
peptone.  The  pepsin  is  not  improved  by  these  additions  ;  they  are, 
in  fact,  mere  unavoidable  impurities,  without  which  the  pepsin 
would  be  of  greater  strength.  Hitherto  it  has  been  impossible  to 
produce  an  entirely  pure  pepsin.  The  scraped  stomachs  contain  a 
large  amount  of  mucus  and  skin  tissue,  the  powdered  inner  coatings 
also  contain,  besides  traces  of  mucus,  a  large  amount  of  skin  tissue. 
The  pepsin  prepared  by  Scheffer's  method  contains  salt  and  inert 
albuminous  matter,  while  the  scale  and  crystal  pepsins  contain 
mucus,  syntonin  and  peptone. 
Purification  of  Pepsins. — For  purifying  the  pepsins  made  by  pre- 
cipitation with  salt,  or  by  dissolving  the  inner  skins  of  the  stomachs 
and  scaling  the  concentrated  solutions,  various  suggestions  have 
been  made  from  time  to  time,  with  a  view  to  reduce  the  amount  of 
unavoidable  impurities.    Sulphate  of  soda  has  been  proposed  as  a 
