564  Opsonic  Theory  and  Tuberculosis.  {ab£^S" 
feel,  very  presumptuous  in  undertaking  a  task  to  which  I  fully 
appreciate  I  can  do  but  feeble  justice.  My  personal  experience  on 
opsonins  in  connection  with  tuberculosis  is  comparatively  limited, 
more  of  my  work  having  been  done  with  the  organisms  responsible 
for  the  mixed  infections.  However,  since  I  shouldered  the  respon- 
sibility of  this  paper,  and  you  will  forbear  with  me  a  short  time,  I 
will  attempt  in  as  brief  a  manner  as  possible  and  as  lucidly  as  my 
literary  abilities  will  permit,  to  give  you  an  insight  at  least  into  the 
subject. 
Inasmuch  as  Dr.  Hitchens  has  explained  so  fully  what  is  meant 
by  "  Opsonin  "  I  will  not  reiterate  it.  Neither  will  I  tax  your  minds 
with  the  various  theories  of  immunity,  of  which  there  are  a  great 
number — some  simple,  others  intricate.  Any  of  you  who  are  thirst, 
ing  after  such  knowledge  and  are  desirous  to  wrestle  with  these 
problems  I  can  only  refer  to  the  many  works  on  the  subject  of 
past  and  recent  times.  I  would  not  touch  upon  the  technique 
of  estimating  the  opsonic  index  in  tuberculous  patients  were  it  not 
for  the  fact  that  in  working  with  the  Bacillus  tuberculosis,  methods 
are  somewhat  different  than  are  those  when  other  bacteria  are 
employed.  To  be  sure  the  preparation  of  the  blood  cream  is  the 
same  in  both  instances ;  the  contents  and  proportion  of  each  in 
the  opsonizing  tubes  do  not  differ,  to  the  exclusion  of  the  organism 
used;  the  process  of  mixing  is  the  same,  as  is  also  the  making  of 
the  smears.  On  the  other  hand,  the  preparation  of  the  emulsion  is 
a  more  difficult  and  tedious  task  than  is  the  case  with  the  other 
bacteria  if  a  suitable  one  is  to  be  obtained ;  special  staining  is 
required  and  the  time  of  incubation  is  more  prolonged.  Let  me 
digress  one  moment  and  say  a  few  words  here  as  to  the  mixing. 
The  method  adopted  by  Wright  has  been  explained  to  you  by 
Dr.  Hitchens.  It  seems  to  me  that  the  method  while  insuring 
thorough  incorporation  is,  except  in  very  skilled  hands,  performed 
at  the  risk  of  introducing  many  air  bubbles  to  the  tube,  thus 
interfering  with  proper  phagocytosis.  I  have  observed  some 
laboratory  workers  indeed,  who,  in  order  to  avoid  this  exasperating 
complication,  have  abstained  from  completely  emptying  the  tube 
at  each  compression  of  the  rubber  nipple,  which  would  of  neces- 
sity be  fruitful  of  errors.  To  overcome  this  I  have  devised  a 
tube  which  I  have  found  extremely  satisfactory.  It  is  easy  to 
manipulate;  thorough  mixture  is  secured,  and  it  obviates,  or  at  least 
