AnMJai-ch,f9ho7.rm  }     The  Opsonins  and  Bacterial  Vaccines.  145 
or  Jenner's  stain,  is  employed.  Carbol-fuchsin  is  employed  for  the 
tubercle  bacilli. 
METHOD  OF  OBTAINING  OPSONIC  INDEX. 
Special  capillary  pipettes,  graduated  into  equal  divisions,  are  re- 
quired ;  then  by  means  of  a  rubber  tube  or  bulb  equal  quantities  of 
washed  corpuscles,  bacterial  emulsion,  and  patient's  serum  are  taken 
up,  and  all  blown  out  upon  a  glass  slide  and  thoroughly  mixed.  The 
mixture  is  then  drawn  up  in  a  small  pipette,  sealed,  and  placed  in 
an  incubator  of  the  ordinary  type,  or  preferably  in  an  opsonic  incu- 
bator as  proposed  by  Freeman;  it  is  heated  to  37 0  to  400  C.  for 
fifteen  minutes.  A  similar  tube  is  prepared,  except  that  the  normal 
serum  or  "  Pool  "  is  employed  instead  of  the  patient's  serum.  At 
the  end  of  fifteen  minutes  the  smears  on  microscopical  slides  are 
made  from  each  tube,  fixed,  and  stained.  A  good  field  is  sejected, 
one  containing  many  leucocytes,  the  number  of  germs  counted  in 
the  first  fifty  or  hundred  observed,  and  an  average  per  leucocyte 
determined.  If  the  average  in  the  mixture  containing  the  normal 
serum  is  two,  we  would  say  that  the  normal  opsonic  index  is  two, 
and  if  the  mixture  containing  the  patient's  blood  serum  is  one  per 
corpuscle,  we  would  say  that  his  index  was  one-half,  etc. 
'Wright  and  his  pupils,  as  the  result  of  numerous  observations, 
classify  diseases  due  to  bacterial  infections  : 
(1)  "  Diseases  in  which  the  bacterial  process  is  strictly  localized  " 
or  "  shut  off  from  the  lymph  and  blood  circulations."  Furunculosis, 
lupus,  tuberculosis,  etc.,  in  fact  most  chronic  infections,  belong  to  this 
class.  "  In  this  class  the  opsonic  index  of  the  blood  is  persistently 
below  normal,  owing  to  the  absence  of  immunizing  stimuli." 
(2)  "  Diseases  in  which  the  bacterial  process  is  but  loosely  shut 
off,  especially  from  the  lymph  circulation."  In  these,  usually  acute, 
infections  immunizing  products  from  the  invading  bacteria  from 
time  to  time  get  into  the  circulation,  and  the  opsonic  index  may  be 
normal  or  above  or  below  normal.  Good  examples  of  this  class 
are  tuberculous  joints,  etc. 
(3)  "  Diseases  in  which  the  bacterial  infection  is  in  the  blood 
stream."  In  this  class  belong  acute  infectious  diseases,  septicemia, 
endocarditis,  Malta  fever,  etc.  In  these  "  the  opsonic  index  is 
generally  below  normal." 
Wright  and  Douglas  lay  down  the  following  general  principles 
for  treating  cases  of  bacterial  infections : 
