140  Manufacture  of  Pepsin.  {AmMJa0rch.Km* 
THE  MANUFACTURE  OF  PEPSIN  AND  DETERMINATION 
OF  ITS  PROTEOLYTIC  POWER.1 
Pepsin,  the  active  principle  of  the  gastric  secretion,  is  an  albumin- 
ous principle  secreted  by  glands  imbedded  in  the  tissue  of  the  inner 
coating  of  the  stomach ;  it  is  a  colloid,  differing  from  ordinary 
albumin  in  its  behavior  with  nitric  acidv  not  giving  the  yellow 
xanthoproteic  reaction,  and  is  soluble  in  water  and  glycerin.  When 
in  solution  it  is  destroyed  by  boiling,  by  strong  alcohol,  by  alkalies, 
and  by  most  metallic  compounds.  Pepsin  acts  on  nitrogenous 
matters  only  when  in  slightly  acid  solutions.  At  present  it  is  almost 
exclusively  prepared  from  pigs'  stomachs,  the  digestive  secretions 
of  the  sheep,  calf  and  ox  being  less  active.  Various  processes  of 
making  pepsin  have  been  and  are  still  followed  ;  none  of  them  yields 
an  absolutely  pure  product,  though  the  digestive  power  of  some  kinds 
of  pepsin  is  very  high  indeed.  Ten  years  ago  an  article,  possessing 
a  digestive  power  of  fifty  times  its  weight,  was  considered  very  good, 
but  now  it  is  expected  that  I  grain  of  pepsin  should,  under  certain- 
conditions,  digest  2,000  grains  of  hard-boiled  white  of  egg. 
Commercial  pepsin  was  first  prepared  by  cutting  up  pigs'  stomachs 
into  small  pieces,  macerating  these  in  slightly  acidulated  water, 
filtering  the  solution,  and  evaporating  it  at  a  low  temperature  to 
dryness.  Next,  it  was  thought  to  improve  the  process  by  taking 
the  filtered  pepsin  solution  and  precipitating  it  by  means  of  basic 
acetate  of  lead,  decomposing  the  precipitate  by  sulphuretted 
hydrogen,  and  evaporating  the  filtrate,  either  by  itself,  or  with  the 
addition  of  sugar  of  milk.  These  processes  were  naturally  tedious, 
the  pepsin  so  prepared  had  almost  always  a  putrid  odor,  it  was 
liable  to  contain  lead  and  other  impurities,  and  it  possessed  very 
little  digestive  power. 
Beal 's  Process. — Dr.  Lionel  Beal  suggested  taking  the  inner  coat 
of  the  fresh  pig's  stomach,  and  after  well  washing  and  cleansing  it, 
to  scrape  it  with  a  blunt  knife,  and  dry  the  viscid  fluid  so  obtained 
on  glass  plates  ;  to  afterwards  treat  it  with  benzol,  ether  or  chloro- 
form, to  extract  fat,  again  dry  it  and  reduce  to  fine  powder.  This 
process  is  accepted  and  published  in  the  British  Pharmacopoeia.  The 
pepsin  so  prepared  is  described  as  sparingly  soluble  in  water  ;  but 
since  the  active  principle  of  pepsin  itself  is  soluble,  that  does  not 
1  Pharmaceutical  Journal  and  Transactions,  January  21,  1893,  p.  588. 
