332  Serum  Treatment  of  Hay  Fever.      { Am* juiyr;i905arm' 
the  rye  pollen  protein  is  determined,  of  which  one  drop  instilled  into 
the  conjunctival  sac  will  just  cause,  within  a  few  minutes,  a  subjective 
and  objective  reaction.  This  may  be  termed  the  maximum  dosage. 
Then  a  series  of  toxin  and  antitoxin  mixtures  is  so  arranged  that 
equal  volumes  of  diluted  serum  are  added  to  definite  quantities  of 
a  doubly  concentrated  solution  of  toxine.  The  mixture,  which  just 
evades  irritating  the  patient's  eyes,  is  designated  the  neutral  mixture. 
The  effectiveness  of  the  serum  is  therefore  determined  by  the  de- 
gree of  dilution  which  is  required  to  neutralize  the  plain  toxin  solu- 
tion. 
This  determination  following  the  very  numerous  tests,  is  not 
affected  by  errors  exceeding  10  per  cent. 
Now,  from  the  horse,  which  has  proven  its  high  value,  a  suitable 
quantity  of  blood  is  withdrawn — at  least  ten  days  after  the  last  in- 
oculation— and  worked  for  its  serum  properties. 
The  horses  which  are  used  for  this  purpose,  being  under  the  con- 
stant care  of  a  veterinary  surgeon,  all  manipulations  are  made  under 
the  strictest  aseptic  precautions.  The  antitoxin  contained  in  the 
serum  is  under  constant  surveillance,  and  hence  it  is  possible  to 
obtain  an  absolute  harmless  preparation  and  one  constant  in  its 
effectiveness.  Now  with  regard  to  the  method  of  using  the  serum, 
it  was  emphasized  from  the  beginning  that  this  medium  was  not  in- 
tended for  subcutaneous  use,  but  only  for  external  application  at  the 
site  of  the  disease.  Neither  has  the  time  yet  arrived  when  the  sub- 
cutaneous method  of  treatment  can  be  recommended;  for  even 
though  favorable  results  have  been  obtained  in  very  bad  cases,  such 
results  persist  not  more  than  two  or  three  days  at  the  most  and  even 
then  but  a  partial  immunity  is  obtained.  Besides,  the  disagreeable 
feature  of  subcutaneous  injection  would,  for  most  people,  outweigh 
their  advantages.  On  the  other  hand,  the  local  treatment,  which 
consists  in  the  direct  application  of  the  serum  to  the  afflicted  mucous 
membrane  of  the  eyes,  nose,  or  pharynx,  has  proven  efficacious. 
The  serum  is  used  either  in  the  fluid  form  or  in  the  form  of  a  pow- 
der which  has  been  dried  in  a  vacuum. 
If  the  fluid  form  is  used,  the  addition  of  a  suitable  preservative 
must  not  be  omitted.  Carbolic  acid  may  be  added  for  this  purpose 
in  the  proportion  of  I  to  400. 
In  a  comparative  test  of  various  suitable  mediums  for  preserving 
the  serum  and  which  would  not  be  irritating  to  the  mucous  mem- 
