154 
Antitoxin, 
<  Am.  Jour.  Pharm. 
I      March,  1895. 
The  next  step  is  to  render  the  blood  of  some  animal  immune  to 
this  poison,  by  injecting  subcutaneously  small  quantities  at  a  time 
until  the  desired  result  is  attained.  The  cow,  sheep  or  goat  may 
be  used  for  this  purpose,  but,  for  various  reasons,  the  horse  has  been 
selected  ;  he  is  not  so  seriously  affected  by  the  poison ;  that  is,  he 
does  not  contract  the  disease ;  then  he  is  usually  healthy,  and  will 
yield  a  comparatively  large  quantity  of  blood  at  one  time. 
The  treatment  of  the  horse  consists  in  injecting  a  small  quantity 
of  the  toxin  into  the  upper  part  of  the  neck,  beginning  with  such 
a  small  amount  as  to  produce  no  ill  effects.  If  the  solution  is  too 
active,  its  strength  may  be  reduced  by  exposure,  for  a  few  minutes, 
to  a  temperature  of  65  °  to  700  C,  or  it  may  be  treated  with  a 
small  quantity  of  solution  of  iodine  in  potassium  iodide.  In  the 
course  of  a  few  days,  the  strength  and  frequency  of  the  injections 
are  gradually  increased,  and  in  a  few  weeks,  the  animal  is  able  to 
bear  large  doses  without  injury.  When  this  condition  has  been 
reached,  the  horse  is  bled  to  the  extent  of  one  to  one  and  one-half 
litres  ;  as  much  as  ten  litres  have  been  drawn  from  one  horse  during 
two  days,  and  the  average  for  each  animal  varies  from  twenty-five 
to  fifty  litres  a  month.  Dr.  Behring  has  stated  that  a  horse  from 
which  he  had  drawn  blood  at  frequent  intervals  during  four  years, 
remained  in  good  physical  condition.  After  the  horse  has  been 
immunized,  he  may  be  so  retained  by  occasional  injections  of  the 
toxin.  As  a  rule,  twenty  days  are  allowed  to  elapse  after  the 
injection  before  blood  is  drawn. 
When  the  blood  is  withdrawn,  it  is  cooled  and  allowed  to  stand 
until  clotting  takes  place,  whereby  the  fibrin  and  corpuscles  are 
removed  and  a  clear  serum  is  obtained. 
Properties. — This  anti-diphtheric  serum  is  what  is  popularly 
known  as  antitoxin.  It  is  a  clear,  yellowish-colored  liquid,  and 
may  be  concentrated  to  dryness  in  a  vacuum  without  undergoing 
change.  It  is  preserved  by  drying  in  this  manner,  or  by  the  addi- 
tion of  carbolic  acid.  It  is  also  sometimes  preserved  by  the  addi- 
tion of  a  small  lump  of  camphor  to  each  bottle  of  the  liquid.  The 
dried  antitoxin,  when  wanted  for  use,  is  dissolved  in  eight  or  ten 
parts  of  water. 
Age  is  said  to  improve  the  serum,  by  lessening  its  tendency  to 
cause  in  some  patients  a  slight  eruption  of  the  skin. 
Administration. — Antitoxin  is  administered  subcutaneously  from  a 
