626  DiastatiG  Ferment  of  Bacteria.         { ^""bec"  iss?*'"'" 
disposal,  and  this  ferment  is  incapable  of  changing  albumin  into 
peptone,  just  as  in  the  case  of  diastase.  It  is  well  known  that  the 
pepsin  of  gastric  juice  acts  only  in  an  acid  medium.  The  plant  juices 
which  possess  a  diastatic  property  exhibit  likewise  a  more  or  less  acid 
reaction,  so  that  as  Baranetzky  assumes,  the  co-operation  of  an  acid  in 
the  case  of  diastase  is  a  necessary  condition  of  its  activity.  The  solu- 
tions in  which  starch  in  one  or  another  form  was  submitted  to  the 
action  of  bacteria  were  always  slightly  acid,  due  to  the  presence  of 
acid  ammonium  phosphate,  and  when  the  solutions  were  purposely 
made  neutral,  the  process  of  starch  transformations  went  on  more 
slowly.  Detmer  some  time  since  has  shown  that  addition  of  small 
quantities  of  citric  acid  to  a  solution  containing  diastase,  hastens  its 
action  on  starch.  The  author's  observations  are  in  harmony  with  this^ 
but  in  addition  show  that  the  process  of  starch  transformation  by 
Jbacteria  is  capable  of  going  on  in  the  absence  of  acid,  and  that  the 
bacteria  do  not  yield  any  acid  in  the  process.  The  results  of  the 
author's  researches  may  be  briefly  recapitulated. 
1.  Bacteria  are  capable  of  acting  on  starch,  whether  in  the  solid 
state,  as  paste,  or  in  solution,  in  a  manner  analogous  to  diastase. 
2.  As  in  the  case  of  diastase,  different  kinds  of  starch  are  attacked 
by  bacteria  with  different  degrees  of  rapidity. 
3.  The  action  of  bacteria  on  starch  is  manifested  only  in  the  absence 
of  other  sources  of  carbon  nutriment,  and  when  access  of  air  is  not 
prevented. 
4.  The  action  of  bacteria  on  starch  is  effected  by  a  ferment  secreted 
by  them,  and  which,  like  diastase,  is  soluble  in  water,  but  precipitable 
by  alcohol. 
5.  This  ferment  acts  precisely  as  diastase  in  changing  starch  into  a 
sugar  capable  of  reducing  cupric  oxide,  but  not  possessed  of  peptonising 
properties. 
6.  The  ferment  itself  is  also  capable  of  acting  on  starch  in  the 
absence  of  oxygen. 
7.  The  ferment  is  secreted  by  the  bacteria  also  in  neutral  solution 
of  starch,  and  exerts  its  influence  under  these  conditions. 
8.  This  influence  is  expedited  in  slightly  acid  solutions. 
The  author  concludes  his  paper  with  speculations  as  to  the  condi- 
tions under  which  bacteria  are  capable  of  generating  this  amylolytic 
(diastatic)  ferment,  instead  of  the  ordinary  peptonising  one. — Jour. 
Chem  Soc,  1883,  p.  390;  Zeitschr.  Physiol  Chem.,  vi,  287-329. 
