and  the  Prevention  of  Rot. 
297 
1.  There  must  be  fluke-eggs  on  the  ground. 
2.  There  must  be  wet  ground  or  water  during  the  warmer 
weather  for  the  eggs  to  hatch  in. 
3.  A particular  snail  called  Limnceus  truncatulus  must  be 
present. 
4.  Sheep  or  other  animals  must  be  allowed  to  feed  on  the 
same  ground,  without  proper  precautions  being  taken. 
If  any  one  of  these  conditions  remains  unsatisfied  there  can 
be  no  fluke-disease  or  liver-rot  in  the  locality.  Let  us  consider 
these  conditions  in  detail. 
ls£  Condition.  There  must  be  fluke-eggs  on  the  ground. — We 
have  already  seen  that  the  fluke  whilst  in  the  liver  of  the  sheep, 
rabbit,  or  other  animal,  produces  vast  quantities  of  minute  eggs, 
and  that  these  pass  into  the  intestines  and  are  distributed  in 
myriads  wherever  the  droppings  fall.  So  that  wherever  fluked 
sheep  are  kept,  there  wre  shall  have  fluke-eggs. 
In  some  districts  the  fluke  is  always  to  be  found,  though  in 
dry  seasons  it  may  become  scarce.  Still  a few  exist,  and  these 
are  quite  sufficient  to  keep  up  the  breed  until  a wet  season 
occurs,  when,  under  the  favourable  influence  of  moisture,  they 
increase  so  rapidly  as  to  produce  a devastating  outbreak. 
But  the  fluke  disease  may  appear  in  quarters  where  it  wras 
previously  unknown,  and  surprise  is  frequently  expressed  at  the 
way  in  which  it  suddenly  breaks  out  in  isolated  flocks.  The 
infection,  however,  may  be  introduced  in  many  ways.  Eggs  may 
be  brought  in  manure  ; or  adhering  to  the  feet  of  men,  horses, 
or  dogs  ; or  they  may  be  conveyed  by  running  water,  and  espe- 
cially by  floods.  Rabbits  and  hares,  too,  have  much  to  answer 
for  in  distributing  the  parasite.  The  same  account  is  given 
everywhere  of  the  way  in  which  rabbits  suffer  from  rot,  and  in 
some  neighbourhoods  about  Oxford  they  wrere  almost  exter- 
minated by  it  in  1879-80.  I have  received  on  several  occasions 
fluked  rabbits,  and  have  known  them  to  contain  each  as  many  as 
forty  or  fifty  flukes.  Wherever  they  go,  and  they  often  wander 
far  from  home,  the  eggs  of  the  fluke  are  distributed  in  their 
droppings.  In  a case  where  infection  had  suddenly  broken  out 
in  an  isolated  flock  of  sheep  at  Wytharn,  near  Oxford,  I was 
able  to  show  that  the  rabbits  from  the  neighbouring  woods  had 
introduced  the  disease. 
So  wonderfully  fertile  is  the  liver-fluke  that,  if  every  egg 
were  safely  hatched  out  and  the  full  average  multiplication  in 
the  snail  were  attained,  a single  rotten  sheep  might  pass  enough 
eggs  to  eventually  give  the  rot  badly  to  all  the  sheep  in  England, 
some  thirty  millions  in  number.  Fortunately  the  chances  are 
very  greatly  against  any  flukes  being  reared  from  any  particular 
egg.  Still  we  must  do  all  we  can  to  increase  these  adverse 
