Am.  Jour.  Eharm.  ) 
August,  1911.  J 
Action  of  the  Enzymes.- 
373 
The  hydrochloric  acid  is  directed  to  be  much  more  dilute  than 
that  originally  used,  as  it  has  been  found  to  give  a  lighter  and  a 
finer  precipitate. 
The  suspension  should  not  be  prepared  long  before  it  is  to  be 
used.  At  least  an  hour,  however,  should  be  allowed  for  its  prepara- 
tion, and  the  operator  should,  under  no  circumstances,  be  hurried. 
The  services  of  an  assistant  to  handle  the  pipettes  will  materially 
shorten  the  time  required. 
Phenolphthalein  paper  is  much  more  certain  in  determining  the 
reaction  than  litmus.  Red  litmus  does  not  change  till  a  great  excess 
of  alkali  has  been  added.  Blue  Htmus  is  more  sensitive  but  not  so 
sharp  in  distinction  as  phenolphthalein.  When  neutral  to  the  latter, 
the  preparation  slightly  deepens  the  color  of  blue  litmus.  This  seems 
to  be  the  proper  end  point,"  as,  when  more  acid  is  added  till  just 
neutral  to  litmus,  the  suspension  of  the  precipitate  is  not  so  perfect. 
SOME  THOUGHTS  ON  THE  ACTION  OF  THE  ENZYMES, 
WITH  SPECIAL  REFERENCE  TO  THE  NATURE 
OF  PEPSIN.^ 
By  James  E.  Hancock. 
Ever  since  the  discovery  of  the  enzymes,  physiological  chemists 
have  tried  to  explain  the  transformations  that  occur  under  their 
influences  and  to  systematically  reason  why  these  changes  should  be. 
One  theory  and  then  another  has  been  suggested,  each  of  which  has 
been  based  upon  certain  peculiarity  of  reaction  that  has  happened 
under  the  particular  investigator's  notice.  The  study  is  fascinating 
because  metabolism  generally  is  a  physiological  process  that  cannot 
be  even  approximately  understood  until  the  actions  of  enzymes  are 
comprehended.  Every  problem  in  the  growth  and  dissolution  of 
plants  and  animals,  and  especially  in  the  transferences  of  energy, 
is  connected  in  some  way  or  other  with  the  action  of  enzymes. 
Plants,  with  very  few  exceptions,  acquire  their  food  from  the  soil 
and  from  the  air.  By  the  action  of  enzymes  under  favorable  in- 
fluences of  light,  heat  and  moisture,  the  organic  materials  that  are 
thus  absorbed  are  elaborated  into  complex  compounds,  consisting 
*  Read  at  a  meeting  of  the  Maryland  Pharmaceutical  Association,  June, 
1911. 
