Annual  Report  for  1910  of  Royal  Veterinary  College.  297 
blood  stream  of  a pregnant  cow,  but  no  great  interest  attaches 
to  such  an  entirely-  non-natural  method  of  infection.  Much 
more  important  is  the  fact  that  the  administration  of  infective 
material  by  the  mouth  determined  infection  of  pregnant  cows 
in  three  out  of  four  experiments.  Indeed  the  experiments 
indicated  that  the  chances  of  successful  infection  are  some- 
what greater  when  the  bacilli  are  introduced  into  the 
alimentary  canal  than  when  they  are  directly  introduced 
into  the  genital  passages.  Having  regard  to  all  the  circum- 
stances, it  therefore  appears  to  be  reasonable  to  conclude  that 
by  far  the  commonest  method  of  natural  infection  in  a cow-shed 
is  the  ingestion  of  bacilli  which  have  escaped  from  the  body 
of  a previously  diseased  animal.  It  would  not  be  justifiable  to 
deny  that  infection  may  sometimes  be  brought  about  through 
the  accidental  introduction  of  infective  material  direct  into  the 
genital  passages  while  the  cow  is  lying  down,  but  it  appears  to 
be  more  than  likely  that  that  method  of  infection  is  of  quite 
secondary  importance  as  compared  with  infection  by  the  mouth. 
It  is  now  possible  to  understand  the  futility  of  attempting 
to  check  the  spread  of  the  disease  in  an  infected  cow-shed  by 
disinfection  of  the  external  genitals  and  hind  quarters  of  the 
healthy  animals.  One  must  now  reckon  with  the  fact  that 
when  a herd  of  pregnant  cows  contains  one  or  more  infected 
animals  no  amount  of  trouble  taken  to  disinfect  the  hind 
quarters  of  the  healthy  animals  can  be  expected  to  check  the 
spread  of  the  disease,  though  frequent  cleansing  and  disin- 
fection of  the  floor  of  the  cow-shed  may  help  in  that  direction. 
The  Committee  in  their  first  report  also  discuss  the 
possible  role  of  the  bull  in  the  transmission  of  the  disease, 
and,  while  not  denying  that  a bull  may  mechanically  transfer 
the  bacilli  from  a diseased  to  a healthy  cow  when  the  two 
different  services  are  separated  by  only  a slight  interval,  they 
incline  to  the  view  that  this  also  is  an  exceptional  method  of 
infection. 
The  further  researches  of  the  Committee  were  devoted  to 
ascertaining  (1)  the  most  reliable  methods  of  diagnosing  the 
disease,  and  (2)  the  possibility  of  immunising  healthy  animals 
against  infection. 
The  observations  made  by  the  Committee  show  that  it  is 
a comparatively  easy  matter  to  determine  whether  any  given 
case  is  one  of  epizootic  abortion  when  material  for  examination 
can  be  obtained  at  the  time  of  abortion  or  within  a day  or  two 
afterwards.  When  one  has  the  opportunity  to  stand  by  at  the 
act  of  abortion  in  a case  of  the  contagious  disease,  there  is  never 
any  difficulty  in  finding  and  identifying  the  specific  bacilli, 
either  in  the  discharge  which  comes  away  at  the  moment,  or 
in  the  substance  of  the  foetal  membranes,  or  in  the  body  of  the 
