AVa?ch',r9of.rm'}       Nature  and  Action  of  Toxins.  105 
There  is  still  another  important  fact  which  must  be  mentioned  : 
Experimental  data  show  that  the  intermediary  body  is  not  necessary 
for  the  combination  of  the  receptor  with  the  toxic  complement.  The 
receptor  may  combine  with  either  the  toxic  complement  or  the  inter- 
mediary body  alone  ;  in  this  case  no  toxic  action  will  result.  In 
order  to  have  a  toxic  action,  the  receptor  must  combine  simulta- 
neously with  both  these  elements.  In  other  words,  we  must  con- 
clude that  the  receptor  has  two  unsaturated  affinities  (hence  "  ambo- 
ceptor "),  whilst  the  toxic  complement  and  the  intermediary  body 
have  each  only  one  affinity.  If  only  one  of  the  affinities  of  the 
receptor  is  saturated,  either  by  an  intermediary  body  or  by  a  toxic 
complement,  this  will  not  interfere  seriously  with  the  biogen  ;  but  it 
both  are  saturated  simultaneously  by  a  toxic  complement  and  by  an 
intermediary  body,  the  receptor  is  rendered  useless,  as  already 
explained.  And  if  the  toxic  molecules  are  sufficiently  numerous  to 
saturate  most  or  all  of  the  receptors,  the  biogen  must  be  destroyed, 
since  unsaturated  receptors  are  essential  to  its  nutrition,  and  thus  to 
its  lite.  Since  the  biogen  contains  a  very  large  number  of  actual  or 
potential  receptors,  the  result  of  the  saturation  of  one  or  a  few  of 
these  is  not  necessarily  fatal  to  the  biogen.  Indeed,  as  may  be  seen 
in  tissues,  a  small  injury  often  serves  as  a  stimulant,  and  in  this  case 
it  leads  the  biogen  to  regenerate  the  lost  receptors.  It  even  goes 
further  and  regenerates  these  receptors,  or  whichever  of  its  groups 
have  been  lost  in  excess,  and  discharges  these  into  the  exterior,  into 
the  serum.  The  serum  charged  with  these  receptors  has  now  the 
power  to  bind  toxins,  and  is  therefore  "antitoxic." 
The  facts  will  be  much  more  readily  understood  it  we  substitute 
symbols  for  the  terms,  and  represent  the  reactions  as  we  would  in 
chemistry. 
Let  B  =  the  main  biogen  molecule ;  R<  one  of  its  receptors 
with  its  two  unsaturated  affinities  ;  —  T  the  toxic  complement ;  —  i 
the  intermediary  body,  each  with  one  affinity.  The  normal  biogen 
molecule  would  then  stand  :  B  .  R<  ;  the  poisoned  molecule 
B  •  R<1'  or  possibly  B  •  R(  I 
1  \T 
The  following  cases  occur  : 
(a)  If  the  toxin  contains  both  i  and  T,  it  can  enter  directly  into 
combination  with  B  •  R<.  If  an  antitoxin  is  produced,  this  must 
consist  of  R<. 
