ADecemberf?9T3m'}      Enzymes  and  Their  Importance.  557 
presence  of  oxygen  and  peroxides;  these  are  extensively  present  in 
medicinal  plants,  and  the  guaiacum  blue  reaction  is  due  to  their 
action.  The  catalases  decompose  hydrogen  peroxide  in  oxygen  and 
water,  while  the  reductases  are  responsible  for  reductions  and  also 
play  a  part  in  the  living  cell. 
There  is  scarcely  a  living  plant-cell  free  from  enzymes;  peroxy- 
dases  and  catalases  especially  appear  to  be  present  everywhere,  and, 
as  already  mentioned,  very  frequently  several  enzymes  of  often 
antagonistic  properties  are  present  in  the  same  cell.  Ten  enzymes 
have  been  isolated  from  the  liver,  and  five  enzymes  from  the  bark 
of  the  horse-chestnut — viz.,  three  different  oxydases,  one  catalase 
and  an  anaeroxydase.  The  changes  which  the  plant  undergoes  post 
mortem  in  its  transformation  into  a  drug  are  of  special  interest  to 
pharmacognosy ;  here  we  have  the  phenomenon  that,  after  separation 
from  the  plant,  many  parts  undergo  considerable  changes,  particu- 
larly of  a  chemical  nature,  such  as  those  which  occur  during  the 
process  of  drying.  In  1888  Professor  Tschirch  established  that 
within  twenty  seconds  of  removing  the  bark  from  Cinchona  succi- 
rubra  it  assumed  a  reddish  color  on  its  inner  surface,  due  to  enzy- 
matic action,  but  if  the  twig  is  put  in  water  at  8o°  C,  on  removing 
the  bark  it  does  not  redden.  In  the  first  phase  of  the  process  the 
glucotannide  present  is  split  up  by  a  glucosidase,  and  in  the  second 
phase  the  aglucon  thus  produced  is  oxidised  to  the  red  coloring- 
matter  by  an  oxydase.  Vanilla  affords  another  example  of  a  differ- 
ent kind  of  enzymatic  action.  In  1888  Professor  Tsirch  found  that 
on  destroying  the  enzymes  by  alcohol  vapor  no  vanilla  odor  occurs, 
and  Winckel's  experiments  in  1909  proved  that  vanillin  is  excreted 
only  in  non-sterilised  fruits. 
It  may  be  accepted  as  proved  that  in  the  process  of  drying  gluco- 
sides  are  altered  by  the  action  of  enzymes,  while  alkaloids  are  appar- 
ently less  affected.  The  question  now  arises :  What  is  the  effect  of 
drying  on  the  enzymes  themselves?  Bourquelot  found  that  several 
plants  contain  enzymes  when  fresh  only,  and  that  they  disappear 
during  drying  or  on  keeping.  The  most  permanent  enzymes  are 
found  in  such  drugs  as  chicory,  taraxacum,  marshmallow,  the  gums, 
and  the  gum-resins.  Gum  acacia  retains  its  enzymes  for  decades, 
as  is  also  the  case  with  the  laccase  of  Japanese  lacquer,  which,  on 
oxidation,  imparts  that  special  character  to  Japan-ware. 
The  question  as  to  whether  the  enzymes  contained  in  drugs  should 
be  destroyed  and  whether  all  enzymes  possess  a  medicinal  action  is 
