450        Recent  Literature  Relating  to  Pharmacy.  {^l^^'S 
Marshall  also  calls  attention  to  the  work  of  Wood,  Spivey  and 
Easterfield  on  charas,  in  which  they  found  no  alkaloid  whatever. 
Having  observed  that  when  cannabinol  is  left  exposed  to  the  air 
in  a  test  tube  it  gradually  darkens,  commencing  on  the  surface,  the 
author  instituted  a  series  of  experiments,  which  not  only  showed  that 
this  darkening  is  due  to  oxidation  but  that  the  activity  of  canna- 
binol is  thereby  impaired.  He  therefore  infers  that  the  loss  of 
activity  of  Indian  hemp  is  due  to  oxidation  of  the  active  ingredient, 
although  oxidation  of  the  terpene  may  also  have  something  to  do 
with  the  deterioration  of  the  drug.  As  a  result  of  his  observations 
the  author  advises  keeping  cannabis  preparations  well  protected 
from  the  air,  and  if  they  are  to  be  kept  for  any  length  of  time,  her- 
metically sealed  packages  are  to  be  preferred.  In  this  connection 
he  states  that  many  of  the  accidents  which  occur  in  practice  are 
probably  due  to  the  difference  in  activity  between  surface  layers  of 
the  preparation  and  those  lower  down,  or  to  the  difference  between 
recent  preparations  and  those  that  are  old  and  inert  from  exposure. 
F.  Y. 
THE  NATURE  OF  PEPSIN. 
The  veil  of  mystery  which  has  enshrouded  the  subject  of  enzy- 
motic  processes  in  the  human  body  is  beginning  to  fall  beneath  the 
hands  of  careful  investigators.  That  the  pepsin  usually  obtained 
from  the  gastric  juice  and  mucous  membrane  of  various  animals  is 
not  the  essential  enzyme,  but  contains  this  mixed  with  a  number  of 
impurities,  is  conclusively  shown  by  the  latest  researches  of  C.  A. 
Pekelharing  (Hoppe-Seyler*  s  Ztft.  f.  Physiol.  Chemie,  March  20,  1902). 
In  spite  of  laborious  investigation  he  did  not  succeed  in  obtaining 
from  the  gastric  mucous  membrane  a  proteolytic  enzyme  of  con- 
stant composition.  In  hundreds  of  preparations  obtained  from  pigs' 
stomachs,  which  preparations  had  been  submitted  to  repeated  pro- 
cesses of  purification,  it  was  found  that  the  nitrogen  and  hydrogen 
content  were  in  each  case  respectively  constant,  whereas  the  carbon 
and  particularly  the  phosphorus  content  were  subject  to  variation, 
which  indicated  the  presence  of  impurities.  The  longer  the  process 
of  purification  was  carried  out,  the  smaller  was  the  proportion  of 
phosphorus  obtained.  He  was  even  able  to  obtain  a  pepsin  that 
was  phosphorus-free.  The  author  does  not  deny  the  possibility  that 
pepsin  occurs  in  the  gastric-juice  in  combination  with  lecithin, 
nevertheless  he  asserts  that  the  activity  of  the  enzyme  is  independent 
