562  Opsonic  Theory  and  Bacterial  Vaccines.     1  Am- Jour-  Pharm- 
December,  1907. 
to  break  up  all  clumps  (some  organisms  require  special  treatment 
to  secure  this  end),  in  order  that  a  homogeneous  suspension  may  be 
obtained.  To  accurately  measure  the  dose  of  these  vaccines  it  is 
necessary  to  count  the  number  of  bacteria  per  cubic  centimeter. 
This  is  done  by  one  of  Wright's  most  ingenious  methods.  Equal 
volumes  of  blood  and  bacteria  are  measured  by  means  of  a  capillary 
pipette  and  thoroughly  mixed,  after  which  a  drop  of  the  mixture  is 
spread  upon  a  slide  in  a  thin  layer  by  drawing  the  edge  of  another 
slide  over  it.  The  thin  film  thus  prepared  is  fixed  and  stained. 
Under  the  microscope  the  red  blood  corpuscles  and  bacteria  con- 
tained in  a  number  of  fields  from  various  parts  of  the  slide  are 
separately  enumerated.  Knowing  the  number  of  red  corpuscles  in 
one  cubic  centimeter  of  the  blood  used,  the  proportion  between  the 
corpuscles  and  bacteria  being  ascertained  by  this  enumeration,  it 
becomes  a  simple  mathematical  problem  to  calculate  the  number  of 
bacteria  per  cubic  centimeter.  For  example,  in  twenty-five  fields  we 
find  800  red  corpuscles  and  1600  bacteria;  by  one  of  several  well- 
known  methods  we  have  determined  that  there  are  5,000,000  red 
corpuscles  per  cubic  millimeter  or  5,000,000,000  per  cubic  centi- 
meter— then  8co:  1600::  5,000,000,000:  10,000,000,000. 
The  next  step  is  to  dilute  the  thick  suspension  sufficiently  to 
make  each  cubic  centimeter  contain  a  convenient  number  of  bac- 
teria. A  small  percentage  of  liquor  cresolis  comp.  (N.F.)  is  generally 
added  to  prevent  contamination. 
Experience  in  St.  Mary's  Hospital  appears  to  favor  extremely 
small  doses.  Those  published  a  year  or  more  ago  are  much  larger 
than  the  numbers  given  me  by  Professor  Wright  during  the  past 
summer.    These  are  as  follows  : 
Staphylococcus   50,000,000  to  250,000,000 
Streptococcus   -  1,000  000  5.000,000 
Gonococcus  .   500,000  "  2,000,000 
Pneumococcus   10,000,000  "  20,000,000 
Colon  bacillus   5,000,000  "  20.000,000 
B.  pyocyaneus   5,oco,ooo  "  20,000,000 
Micrococcus  neoformans   5,000,000  "  100,000,000 
Micrococcus  catarrhalis   according  to  turbidity. 
The  tuberculins  are  used  for  the  same  purpose  as  bacterial  vaccines 
and  in  practically  the  same  way.  A  description  of  the  method  of 
their  preparation  which  is  quite  different  from  that  of  the  bacterial 
vaccines  would  increase  the  length  of  this  paper  unduly. 
