264 
ON  PEPSINE. 
carefully  scraped  off  with  a  knife,  the  cells  are  bruised  in  a 
mortar,  and  digested  for  twelve  hours  in  distilled  water.  The 
liquid  is  then  filtered,  and  neutral  acetate  of  lead  is  added,  which 
precipitates  peptate  of  lead.  This  precipitate  is  collected  and 
decomposed  by  means  of  sulphuretted  hydrogen,  pepsine  is  thus 
liberated  in  solution,  and  is  separated  from  the  insoluble  sulphide 
of  lead  by  filtration.  This  liquid  represents  a  neutral  gastric 
juice.  It  is,  however,  necessary  that  it  should  be  acid,  and  for 
this  purpose  lactic  acid  is  added  until  the  liquid  exhibits  the  same 
degree  of  acidity  as  a  specimen  of  gastric  juice,  obtained  from 
the  stomach  of  a  dog  by  means  of  a  fistulous  opening.  The 
reason  why  lactic  acid  is  selected  for  this  purpose  will  be  shown 
below.  If  the  artificial  gastric  juice  thus  obtained,  be  evapora- 
ted to  dryness  at  a  gentle  temperature  (it  should  not  exceed  100° 
Fan.),  a  gummy  mass  is  obtained,  which  attracts  moisture  from 
the  air,  and  is  altogether  a  very  unfit  article  either  for  sale  or 
administration.  In  order  to  reduce  it  to  powder,  M.  Boudault 
simply  evaporates  his  artificial  gastric  juice  to  a  syrupy  consist- 
ence, and  to  this  he  adds  dried  starch  in  such  proportion  that 
one  gramme  (15  grains)  shall  be  in  a  position  to  digest  four 
grammes  of  dry  fibrine,  when  the  two  are  submitted  together  in 
the  presence  of  water  to  the  temperature  of  the  human  body. 
The  substance  thus  produced  is  a  fawn-colored  powder,  co- 
hering somewhat  together,  and  possessing  a  peculiar  taste  and 
odor.  It  yields  to  water  the  lactic  acid  and  the  pepsine,  pro- 
ducing a  solution  of  a  yellowish  tint,  with  the  color,  odor,  and 
taste  of  gastric  juice. 
A  solution  of  pepsine — that  is  to  say,  the  neutral  artificial 
gastric  juice — presents  the  following  reactions : — Salts  of  lead 
and  mercury  give  rise  to  precipitates,  which,  when  decomposed 
by  sulphuretted  hydrogen,  reproduce  the  pepsine  with  its  physi- 
ological properties.  Tannin  likewise  precipitates  pepsine,  but 
the  precipitate  has  no  power  whatever  of  digesting  fibrine.  Rec- 
tified spirit  precipitates  the  pepsine  from  its  solution.  This  pre- 
cipitate is  soluble  in  water.  Absolute  alcohol  dehydrates  pepsine, 
and  destroys,  or  at  all  events  greatly  diminishes  its  digestive 
power.  One  property,  however,  which  pepsine  possesses,  which 
is  very  characteristic,  and  which  is  a  fruitful  source  of  failure  in 
its  preparation,  is,  that  at  the  temperature  of  about  120Q  Fah,, 
