428         DISINFECTANTS  IN  ARRESTING  CATTLE  PLAGUE. 
» 
Every  animal  which  showed  the  least  signs  of  disease  was  at 
once  killed.-  He  then  caused  all  parts  of  the  sheds,  which  could 
have  been  in  contact  with  the  animals,  to  be  washed  with  petro- 
leum, and  the  bodies  of  the  cattle  were  afterwards  rubbed  over 
with  a  cloth  soaked  in  the  same  material.  The  farm  servants  had 
orders  to  wash  their  hands,  boots,  &c,  in  a  mixture  of  petroleum 
and  water,  and  to  sprinkle  their  clothes  with  the  mixture,  whilst 
a  little  petroleum  was  added  to  the  animals'  food  and  drink. 
Their  excrements  were  frequently  removed,  and  the  floor 
sprinkled  with  petroleum.  No  dogs  were  admitted  on  any  pre- 
tence. 
For  five  days  these  precautions  were  rigidly  observed,  when 
they  were  somewhat  relaxed.  They  were  attended  with  com- 
plete success,  and  there  is  little  doubt  that,  carried  out  as  rigidly 
in  this  country,  the  same  good  results  would  ensue.  A  copy  of 
M.  Veron's  pamphlet  was  forwarded  to  me,  and  many  experi- 
ments have  been  made  in  consequence.  Petroleum  depends  for 
its  value  upon  a  small  quantity  (1  or  2  per  cent.)  of  either  car- 
bolic acid  or  a  substance  allied  to  it,  and  Dr.  Angus  Smith  has 
shown  that  when  this  substance  is  removed  by  appropriate  means 
the  purified  petroleum  has  no  antiseptic  value.  This  being  the 
case,  no  experiments  on  the  large  scale  were  tried  with  petro- 
leum, as  they  would  necessarily  be  similar,  but  inferior  in  their 
results,  to  those  of  the  tar  acids. 
23.  The  choice  is  therefore  limited  to  the  oxidizing  disin- 
fectants— chlorine  and  ozone,  and  the  antiseptics — sulphurous 
and  the  tar  acids.  These  are  representative  bodies,  and  numer- 
ous trials  have  been  made  with  them  before  coming  to  a  conclu- 
sion as  to  their  respective  merits  ;  the  results  being  embodied  in 
the  following  pages. 
24.  I  am  bound  to  admit  that  the  conclusion  to  which  I 
have  been  forced  to  come  is  quite  opposed  to  my  preconceived 
ideas  on  the  subject.  I  started  with  a  strong  bias  in  favor  of 
chlorine  and  ozone,  but  the  irresistible  force  of  the  arguments 
derived  from  my  experiments  has  caused  me  to  alter  my 
opinion. 
Oxidizing  Disinfectants. 
25.  At  first  sight  nothing  appears  more  perfect  than  the 
