60  New  Method  for  Preparing  Pepsin.    {^ITi,  m™' 
by  which  strong  bodies,  as  mercury,  lead  and  sulphuretted  hydrogen,  are 
alternately  used,  to  prepare  a  substance,  should  or  might  impair  the 
^quality  of  the  product,  is  very  probable.  That  nevertheless  pepsin, 
prepared  by  such  a  method,  has  the  digestive  power,  speaks  for  the 
almost  inexhaustible  strength  of  it. 
Another  point  of  importance  in  my  preparation  I  would  call  atten- 
tion to,  is  that  no  artificial  heat  at  all  is  used,  neither  by  extracting 
the  stomachs  nor  by  drying  the  pepsin,  and  in  my  whole  process  no 
evaporation  is  necessary.  To  evaporate  the  solution  of  a  substance, 
for  which  a  few  degrees  difference  in  heat  decide  between  life  and 
death,  is  a  very  delicate  operation,  which  is  easily  carried  out  for  ex- 
perimental purposes,  but  on  a  larger  scale  is  almost  impossible. 
My  pepsin  differs  from  the  pepsin  described  in  Gmelin's  Handbook, 
principally  by  the  latter  being  easily  soluble  in  water,  while  mine, 
although  very  soluble  in  the  moist  state,  looses  its  solubility  almost 
entirely  by  exsiccation. 
That  pepsin  precipitate,  which,  combined  with  pepton,  I  obtained 
from  the  pepton  solution,  is  more  identical  to  the  pepsin  described  in 
Gmelin's  Handbook  (Volume  8,  Zoochemie),  as  it  is  easily  soluble  after 
having  become  dry,  is  completely  precipitated  by  alcohol,  shows  a 
more  acid  reaction  and  its  clear  solution  becomes  more  turbid  by  ad- 
dition of  hydrochloric  acid  than  the  pure  pepsin. 
To  bring  the  pepsin  into  a  finely  divided  state,  I  preferred  the  use  of 
milk  sugar  to  that  of  starch,  the  substance  generally  used  for  this 
purpose,  particularly  by  the  French  manufacturers  ;  reasoning  that 
sugar  with  its  antiseptic  properties  will  contribute  to  the  stability  of 
it,  while  starch,  particularly  in  the  damp  state,  is  very  apt  to  get 
mouldy,  and  will  then,  as  a  necessary  consequence,  cause  the  decompo- 
sition of  the  pepsin. 
When  first  making  the  commercial  pepsin,  which  I  called  sacchar- 
ated pepsin,  I  aimed  to  make  it  of  such  strength  that  one  grain  of  the 
saccharated  should  correspond  in  its  digestive  power  to  one  teaspoon- 
ful  of  the  liquid  pepsin  (Amer.  Journal  of  Phar.,  January,  1871); 
that  it  can  be  made  of  much  greater  power  I  have  plainly  shown  by 
the  before  mentioned  results. 
As  for  the  precise  strength  that  will  be  best  suited  for  the  human 
stomach,  that  will  have  to  be  determined  by  physiologists.  Accor- 
ding to  Schroeder,  the  normal  gastric  juice  of  man  dissolves  21  per 
<;ent.  of  coagulated  albumen  ;  five  grains  of  saccharated  pepsin,  which 
