66 
The  Function  of  Enzymes. 
/Am.  Jour.  Pharm- 
\   February,  1915. 
Furthermore,  they  may  be  more  or  less  completely  mechanically  pre- 
cipitated with  flocculent  or  bulky  precipitates,  as  by  use  of  phosphoric 
acid  and  lime  water.  Certain  poisons  may  also  inactivate  enzymes. 
Substances  which  kill  living  cells,  like  formaldehyde,  hydrocyanic 
acid,  or  mercuric  chloride,  will  in  general  "  kill  "  enzymes,  providing 
the  solutions  used  are  strong  enough  and  sufficient  time  is  allowed 
for  the  destructive  action.  The  enzyme  has  a  somewhat  greater 
resistance  than  has  the  living  cell,  but  the  difference  is  one  of  degree 
rather  than  of  kind.  In  fact,  so  closely  do  enzymes  correspond  to 
microorganisms  in  behavior  toward  physical  agencies,  poisons,  etc., 
that  we  use  the  same  terminology  in  discussing  them  and  speak  of 
the  "  poisoning  "  or  "  killing  "  of  the  enzyme.  Other  substances,  such 
as  toluene,  chloroform,  and  a  few  others,  permit  enzyme  reaction  but 
restrain  the  activity  of  living  cells,  this  giving  a  differentiation  of 
great  value  in  studying  them. 
Enzymes  also  have  many  properties  in  common  with  the  toxins, 
and,  so  far  as  body  reactions  go,  seem  to  belong  to  the  same  class  of 
organic  compounds.  When  a  toxin  is  injected  in  small  amount  into 
the  body,  certain  chemical  changes  are  set  up,  and  there  is  soon 
formed  a  so-called  antitoxin  which  neutralizes  or  inactivates  the 
toxin.  Similarly,  the  action  of  enzymes  upon  the  tissues  of  the 
living  body  is  effected  by  the  secretion  of  anti-enzymes,  and  the  in- 
jection of  foreign  proteins  into  the  body  may  be  followed  by  the 
manufacture  of  a  "  precipitin  "  which  will  precipitate  that  particular 
protein  and  no  other.  This  specific  action  is  characteristic  of  enzymes 
and  toxins  as  well  as  of  proteins.  In  view  of  the  fact  that  enzymes 
and  toxins  are,  like  proteins,  the  products  of  living  cells,  it  may  not 
be  strange  that  this  similarity  is  found.  However,  we  are  not  able 
to  say  that  enzymes  are  protein  in  character,  but  rather  that  they 
are  found  in  association  with  proteins.  The  purest  enzymes  yet 
prepared  do  not  give  protein  reactions.  Moreover,  mineral  salts 
seem  essential  for  their  action. 
We  may  explain  the  mechanism  of  fermentation  and  putrefac- 
tion changes  on  the  basis  of  the  enzymes,  produced  by  the  inciting 
organisms,  for  in  recent  years  it  has  been  shown  that  the  enzymes, 
carefully  prepared  and  fed  from  living  cells,  will  carry  on  the  same 
changes  with  almost  mathematical  precision.  In  yeast,  for  example, 
Biichner  found  within  the  cells  an  enzyme  which  could  only  be 
extracted  by  grinding  with  fine  sand  and  subjecting  to  enormous 
