98 
ON  THE  PREPARATION  OF  LIQUID  PEPSIN. 
liquid  losing  it  in  the  same  degree  as  the  mucus  precipitates. 
Upon  these  and  subsequent  experiments  I  have  based  the  follow- 
ing formula  for 
Liquid  Pepsin. 
6  pounds  mucous  membrane  of  hogs'  stomach  are  macerated 
in  a  mixture  of 
4  pounds  glycerin, 
4  pints  water  and 
6  ounces  of  pure  hydrochloric  acid, 
for  thirty-six  hours,  after  which  the  mass  is  put  on  a  strainer, 
and  when  the  liquid  has  drained,  the  membrane  is  macerated 
again  with  three  pints  of  water  for  two  or  three  hours,  then 
strained,  and  this  proceeding  repeated  with  smaller  quantities  of 
water  until  ten  pints  of  liquid  are  obtained. 
The  resulting  liquid  will  be  found  mucilaginous,  very  turbid 
and  of  a  strong  disagreeable  odor.  After  standing  a  few  days, 
however,  the  liquid  becomes  limpid,  a  precipitate  of  mucus  forms 
and,  by  filtration,  a  clear  light  straw-colored  liquid  is  obtained, 
possessing  a  faint  and  disagreeable  odor.  Liquid  Pepsin,  proper- 
ly prepared  according  to  the  above  formula,  is  of  such  strength 
that  one  fl.  oz.,  is  capable  of  dissolving  one  and  a  half  drachms 
of  coagulated  albumen,  which  of  all  albuminous  and  fibrinous 
substances  I  considered  the  best  adapted  for  ascertaining  the 
strength  of  an  artificial  gastric  juice.  This  test  was  made  by 
adding  coagulated  albumen,  cut  into  small  cubes,  to  one  fluid- 
ounce  of  liquid  Pepsin,  keeping  the  fluid  at  a  temperature  of 
one  hundred  to  one  hundred  and  five  degrees,  and  shaking  it 
from  time  to  time,  until  the  albumen  was  dissolved.  By  re- 
peated experiments  with  at  first  smaller  quantities  I  found  that 
one  and  a  half  drachms  of  coagulated  albumen  will  dissolve  in 
one  fluid-ounce  of  liquid  Pepsin  in  from  four  to  six  hours.  Care 
must  be  taken  in  conducting  this  test,  that  the  temperature  does 
not  rise  much  higher  than  105°,  which  in  all  probability  would 
injure  the  solvent  power  of  Pepsin,  and  when  heated  to  the  tem- 
perature of  boiling  water  I  have  found  it,  by  actual  experiment, 
to  lose  all  action  on  albumen.  I  would  here  remark,  that 
albumen  boiled  two  days  before  its  use  for  experiments  was  dis- 
solved much  slower  than  when  freshly  coagulated.    Being  now 
