Am"#e°bu^2arm'}^^  Acid  and  New  Boric  Preparation.  97 
by  the  excess  of  the  gelatin  varies  but  slightly,  but  may  be  put  down 
as  o-2.cc.  As  regards  the  process  depending  on  the  precipitation 
of  the  tannin  by  an  ammoniacal  solution  of  zinc  acetate,  previous  to 
titration,  the  author  found  it  to  give  results  far  too  high  and  gene- 
rally untrustworthy,  even  with  solutions  of  pure  tannic  acid. 
ON  BORIC  ACID  AND  A  NEW  BORIC  PREPARATION.1 
By  Dr.  Jaenicke. 
Experiments  were  made  to  determine  (1)  the  power  of  boric  acid 
to  kill  bacteria,  and  (2)  its  capacity  for  preventing  their  develop- 
ment in  animal  fluids.  The  author  tried  the  influence  of  a  saturated 
(four  per  cent.)  solution  of  boric  acid  on  pure  cultures  of  the  Staph- 
ylococcus aureus,  and  also  on  anthrax  bacilli.  These  organisms 
were  placed  in  the  boric  acid  solution,  and  then  at  regular  intervals 
cultivations  in  sterilized  bioth  were  tried,  and  in  some  cases  ani- 
mals were  injected.  The  staphylococcus  could  be  cultivated 
after  eight  days'  immersion  in  the  boric  solution,  and  in  one 
*  case  indeed  after  fourteen,  and  only  after  three  weeks  were  they 
absolutely  killed.  The  susceptible  bacilli  of  .splenic  fever  were, 
after  twenty-four  hours,  still  living,  and  capable  of  infecting  a  mouse. 
They  died  only  after  three  days.  These  experiments  prove  that 
the  disinfecting  property  of  boric  acid  is  so  slight  that  for  practical 
purposes  it  is  of  no  value,  and  that  boric  acid  is  useless  for  the  dis- 
infection of  hands,  instruments,  etc ,  or  for  applying  to  fresh  opera- 
tion wounds. 
On  the  other  hand,  the  power  of  boric  acid  to  prevent  the 
development  and  increase  of  micro-organisms,  and  the  consequent 
production  of  toxines  and  toxalbumins,  etc.,  is  very  considerable. 
The  author  added  sterilized  boric  acid,  in  gradually  increasing  pro- 
portions, to  blood-serum  and  broth,  in  a  series  of  culture  glasses, 
and  then  inoculated  them  with  pure  bacterial  cultures,  keeping  them 
at  370,  and  comparing  the  effects  of  this  proceeding  with  what 
occurred  in  a  control  glass  free  from  boric  acid.  The  development 
of  bacteria  first  took  place  in  this  glass,  then  it  occurred  in  that  con- 
taining the  smallest  amount  of  boric  acid,  and  more  slowly  in  those 
containing  a  larger  amount,  until  at  last  no  change  took  place. 
This  occurred  in  blood-serum  and  broth  containing  Staphylococcus 
aureus,  when  4  to  5  per  cent,  of  boric  acid  was  present ;  in  the  case 
1  Therap.  Monatsh.;  Abstract  from  Med.  Chronicle,  November,  1891. 
