Am'-\iayr'i91i13rm'  ^  Urinary  Antisepsis.  349 
lated  (as  in  the  germicidal  test)  with  one  standard  loop  of  a  twenty- 
four-hour  broth  culture  of  the  colon  bacillus,  immediately  after 
which  o.i  Cc.  of  each  inoculated  dilution  was  plated,  as  proof  that 
the  inoculation  had  been  made,  and  for  the  purpose  of  comparison 
with  a  second  plate  which  was  poured  (o.i  Cc.  again  being  trans- 
ferred) after  the  inoculated  dilutions  had  been  incubated  for  twenty- 
four  hours  at  370  C.  The  contrasting  of  these  two  plates,  poured  at 
twenty-four-hour  intervals  showed  whether  or  not  growth  had  taken 
place  during  the  incubation  period.  The  first  plate  (poured  immedi- 
ately after  inoculation)  usually  showed  about  10,000  colonies, 
roughly  estimated.  A  second  (twenty-four-hour)  plate  which  was 
sterile  or  which  contained  very  few  colonies  (less  than  100)  was  con- 
sidered proof  of  inhibition,  while  a  plate  showing  countless  numbers 
of  colonies  proved  the  absence  of  inhibition.  In  the  vast  majority 
of  instances  the  contrast  between  Plates  1  and  2  was  so  marked 
that  there  could  be  no  possible  doubt.  A  daily  control  of  inoculated 
drug-free  urine  invariably  contained  countless  numbers  of  colonies 
in  the  second  (twenty-four-hour)  plate,  showing  that  normal  urine 
acts  as  a  favorable  culture  medium  for  the  colon  bacillus. 
Phenolsulphonephthalein  and  Salts. 
The  properties  of  phenolsulphonephthalein  itself,  and  of  some 
of  its  metallic  salts  (sodium,  silver,  copper,  mercury  and  barium), 
as  illustrated  in  the  structural  formula  given  in  Fig.  1,  were  first  in- 
vestigated. Phenolsulphonephthalein,  in  its  free  acid  form,  al- 
although  almost  insoluble,  is  nevertheless  germicidal  (against  the 
colon  bacillus,  according  to  the  arbitrary  standard  described  above) 
in  a  dilution  of  1  :  10,000;  that  is,  it  has  about  fifty  times  the  strength 
of  phenol.  In  urine,  however,  even  in  almost  saturated  solution, 
phenolsulphonephthalein  permits  the  growth  and  development  of 
■OH 
-O 
Fig.  1.    Phenolsulphonephthalein  (monosodium  salt), 
the  colon  bacillus.  A  suggested  explanation  of  this  loss  of  power 
is  that  the  water  solution  kills  by  virtue  of  its  acidity  whereas  in 
