Of  the  6  vaccinated  hogs,  Nos.  1600  and  1601,  which  received
only  2h  c.  c.  of  serum  with  the  disease-producing  blood,  became
slightly  sick  after  vaccination;  the  remaining  vaccinated  hogs
which  received  larger  doses  of  serum  showed  no  syin])toins  of  dis-
ea.se,  and  none  of  the  pen  checks  exposed  to  the  vaccinated  hogs
became  sick.  All  of  the  vaccinated  hogs  witii  tlie  pen  checks  were
moved  to  the  (piarantine  j)asture  and  were  there  e\])osed  to  iiog
cholera  approximately  two  months  after  vaccination.  Two  of  the
3  pen  checks  died  as  a  result  of  this  exposure  and  at  autojKsy  tyi)i(al
lesions  of  hog  choh'ra  were  found.  The  third  check  evidently  ])os-
sess<Hl  a  high  degree  of  natural  resistance  to  the  di.sca.sc.  for  it  did
not  become  distinctly  sick  in  the  pasture  nor  in  the  ex])osure  ])en,
where  it  was  placed  later.
4^


PRODUCTION    OF   IMMUNITY   FROM    HOG   CHOL^^A.
EXPERIMENTS   WITH    SERUM   FROM    SCRIBNER    IMMUNES.  45

Two  of  the  6  vaccinated  hogs  died  while  in  the  quarantine  pasture ;
the  remaining  4  did  not  become  sick.  From  the  autopsy  findings
there  seems  to  be  little  room  for  doubt  that  the  death  of  hog  1600,  1
of  the  2  that  died  in  the  quarantine  pasture,  was  due  to  hog  cholera.
