Am'Mayr'iw4arm'}       ^  se  °f  Antitoxins  and  Vaccines.  203 
symptoms  of  the  disease.  This  process  continues  up  to  the  point 
where  the  number  of  typhoid  .bacilli  destroyed  each  day  equals  the 
number  reproduced  in  the  lesion.  This  balance  is  maintained  for  a 
time  until  the  number  of  bacilli  destroyed  exceeds  those  reproduced. 
A  patient  recovered  from  typhoid  fever  has  remaining  in  his 
tissues  a  large  amount  of  typhoid  protein-splitting  ferment,  so  that 
when  typhoid  bacilli  again  gain  entrance  to  his  tissues  they  are  at 
once  attacked  and  destroyed  before  they  have  a  chance  to  develop. 
Obviously  there  is  no  intoxication,  because  the  amount  of  typhoid 
proteins  is  infinitesimal  compared  to  the  amount  necessary  to  result 
in  anaphylactic  shock. 
It  is  now  easy  to  understand  the  action  of  typhoid  vaccine. 
When  we  inject  beneath  the  skin  a  number  of  typhoid  bacilli,  their 
disintegration  is  started  by  the  normal  proteolytic  ferments  in  the 
body.  A  second  and  third  dose  given  at  intervals  of  about  ten  days 
increases  the  quantity  of  specific  typhoid  protein-splitting  ferment. 
The  theory  of  typhoid  immunity  by  means  of  bacterial  vaccines 
applies  equally  to  the  production  of  immunity  to  other  infecting 
bacteria.  The  theory  underlying  the  use  of  bacterial  vaccines  in 
disease  is  based  on  the  fact  that  the  tissues  affected  are  unable  to 
produce  a  sufficient  quantity  of  the  specific  ferment  to  overcome 
the  infection.  The  injection  of  bacterial  proteins  in  a  healthy  part 
of  the  body  leads  to  the  production  there  of  these  antibodies,  which 
are  conveyed  to  the  focus  of  infection  through  the  circulatory  system 
and  thus  assist  the  local  cells. 
It  will  now  be  clear  that  the  requisites  to  success  in  vaccine 
therapy  are  (1)  that  the  vaccine  injected  must  contain  bacterial 
proteins  identical  in  kind  with  those  causing  the  infection,  (2) 
that  the  ferment  produced  locally  must  come  in  contact  with  the 
infecting  bacteria.  For  one  with  proper  training  it  is  not  hard 
to  determine  the  kind  of  bacteria  causing  an  infection  ;  nor  is  it  hard 
to  obtain  either  a  stock  vaccine  representing  these  bacteria  or  to 
prepare  an  autogenous  vaccine  identical  with  them ;  and  it  is  a 
very  simple  matter  to  inject  these  bacterial  suspensions  beneath 
the  skin  of  the  patient. 
If  the  patient  is  not  in  the  last  stages  of  disease,  there  is  not  one 
chance  in  many  thousands  that  his  tissues  will  fail  to  produce  the 
proper  antibodies  or  ferments.  If  the  patient  shows  no  improve- 
ment as  result  of  the  treatment,  it  behooves  the  physician  to  use 
means  by  which  the  ferments  may  be  induced  to  perform  their 
function. 
