130  Bacterial  versus  Vegetable  Toxins.     {AmMardT  Sis""" 
guished  from  antidiphtheria  and  antitetanus  serums,  which  are 
strictly  antitoxic  in  nature. 
Antiricin  may  be  produced  in  exactly  the  same  way  as  an  anti- 
toxin ;  in  fact,  antiricin  might  be  described  as  a  vegetable  antitoxin. 
Rabbits  have  been  immunized  by  gradually  increasing  doses  of  ricin 
until  they  have  obtained  an  immunity  of  5000,  or,  in  other  words, 
,  have  developed  so  much  antiricin  in  their  blood-serum  that  they  are 
not  affected  by  5000  times  as  much  ricin  as  would  have  killed  them 
had  no  preliminary  treatment  been  instituted. 
The  immunity  acquired  for  both  ricin  and  bacterial  toxins  is 
entirely  different  from  the  tolerance  acquired  for  morphine  and 
other  drugs.  According  to  Cushny,  the  latter  is  due  to  the  cells  of 
the  body  becoming  accustomed  to  being  constantly  bathed  in  a  fluid 
containing  the  alkaloid.  The  same  tolerance  is  acquired  by  various 
marine  animals,  which  would  be  killed  if  suddenly  changed  to  fresh 
water,  but  which  are  gradually  acclimatized  if  the  change  is  made 
more  gradually  by  adding  increasing  proportions  of  fresh  water  to 
the  sea  water  of  the  aquarium.  In  the  case  of  ricin  and  bacterial 
toxins  the  immunity  is  due  to  formation  in  the  body  of  a  substance 
which  antagonizes  the  original  poison  and  constitutes  what  is  known 
as  an  antitoxin.  This  antagonistic  substance  circulates  in  the  blood, 
and  can  be  withdrawn  from  the  immune  animal  and  injected  into  a 
second,  which  then  acquires  a  certain  degree  of  immunity,  although 
less  than  that  of  the  first.  Just  as  diphtheria  antitoxin  and  tetanus 
antitoxin  are  antagonistic  only  to  their  respective  toxins,  so  also 
antiricin  is  antagonistic  only  to  ricin  and  does  not  protect  an  animal 
from  any  other  form  of  toxin. 
Various  animal  poisons,  such  as  snake  venom,  spider  toxin,  and 
eel  serum,  have  been  found  to  act  in  a  similar  manner,  although, 
apart  from  bacterial  toxins,  snake  venom  is  the  only  one  used  for 
therapeutic  purposes.  By  means  of  thi$  an  antitoxin  has  been  pro- 
duced which  has  marked  prophylactic  properties  against  snake  bites, 
and  is  used  extensively  in  countries  where  poisonous  snakes  abound. 
In  addition  to  the  vegetable  toxins — ricin,  abrin,  and  crotin — toxins 
have  also  been  obtained  from  poisonous  mushrooms. 
While  antiricin  has  no  practical  therapeutic  value,  yet  it  was 
as  the  result  of  the  study  of  this  remarkably  interesting  substance 
that  Ehrlich  arrived  at  a  practical  method  of  standardizing  the  bac- 
terial antitoxins,  thus  establishing  a  definite  antitoxin  unit  value  for 
these  products. 
