208 
Autogenous  Vaccines. 
Am.  Jour.  Pharm. 
May,  1914. 
diseases,  which  have  long  been  prevalent  in  that  particular  section, 
but  which  when  carried  to  another  section  where  fresh  soil  is 
obtained  immediately  light  up  into  virulent  epidemics.  This  is  seen 
in  the  ravages  of  tuberculosis  among  the  negroes  and  American 
Indians,  and  it  is  seen  conversely  in  the  immunity  from  yellow 
fever  that  has  long  been  enjoyed  by  the  negro. 
Acquired  immunity  is  the  protection  that  is  afforded  an  in- 
dividual who  has  passed  through  an  attack  of  one  disease,  this  con- 
ferring a  greater  resistance  to  that  disease  in  the  future.  This  is 
commonly  observed  in  diseases  like  typhoid  and  yellow  fever.  Ac- 
quired immunity  may  be  either  active  or  passive.  "  The  process 
of  conferring  protection  by  treatment  with  either  an  attenuated 
form  or  a  sublethal  quantity  of  the  infectious  agent  of  a  disease  or 
its  products  is  spoken  of  as  active  immunization,"  because  the 
immunized  individuals  gain  their  power  of  resistance  by  taking 
an  active  physiological  part  in  the  acquisition  of  this  new  property 
of  immunity.  Thus  active  immunity  can  be  acquired  by  repeated 
injections  of  attenuated  cultures,  as  in  Pasteur's  work  in  hog 
cholera;  by  injections  of  sublethal  doses  of  virulent  bacteria,  as 
demonstrated  in  the  protozoon  disease  of  Texas  fever;  by  injections 
of  killed  bacteria,  first  suggested  by  Chauveau.  This  method  of 
active  immunization  with  gradually  increasing  doses  of  killed  bac- 
teria has  been  carried  out  successfully  against  many  bacterial 
diseases.  It  is  particularly  useful  against  those  groups  of  bacteria 
producing  endotoxin;  and,  finally,  by  injections  with  bacterial 
products  from  poisons  excreted  or  liberated  from  the  bacterial  cell 
body.    These  measures  comprise  vaccination. 
Passive  immunity,  on  the  contrary,  is  that  gained  by  the  host 
through  no  active  formation  of  antibodies  on  its  own  part,  but 
rather  accepting  ready  to  hand  the  antibodies  prepared  by  the 
tissues  of  another  species.  The  most  conspicuous  types  of  this  are 
the  antidiphtheritic  and  antitetanic  sera.  These  are  both  designed 
to  meet  bacterial  exotoxins,  and  it  is  this  type  of  sera  that  is  most 
successful.  On  the  contrary,  antigonococcic,  antistreptococcic  sera, 
and  the  like,  which  depend  for  their  activity  on  the  lysin,  opsonin, 
and  other  antibodies  they  contain,  are  not  blessed  with  a  like  thera- 
peutic success.  Allen  states  that  "  these  sera  are  not  always  cura- 
tive ;  indeed,  their  use  during  active  disease  may  not  be  altogether 
free  from  danger.  Thus  the  administration  of  anticholera  or  anti- 
typhoid serum,  which  each  depend  for  their  activity  on  the  lysin 
