14 
required three times as much; that is, 0.009 c. c. to kill a guinea pig. 
Nevertheless, the combining power of the toxine for antitoxin remained 
the same. 
Toxoids are altered toxins. They consist of the 
toxic molecule in which the toxophore group has 
been destroyed, leaving onl}- the haptophore or 
combining group, which while able to satisf^^ the 
combining' affinities of the antitoxin is no longer 
able to poison the protoplasm of the cell. 
The diphtheria bacillus, during the process of its 
growth ^lnd multiplication in the body or in an 
artificial culture medium, produces several poisons, 
one of which is known as the diphtheria toxin. As above stated, the 
diphtheria toxin consists of a toxophore and haptophore group. In 
the bod}" the latter unites chemically with the 
receptors of the cells. T\ffien this takes place 
one of two consequences may result: Either (1) 
the cell is so severely poisoned that it dies, or 
(2) the living molecule of protoplasm is stimu- 
lated so as to excite a defensive action by the 
reproduction of the receptors. Continued stim- 
ulation produced by the periodical injection of 
toxine results in an over production of recep- 
tors which finally loosen and float free in the 
blood serum and body juices. 
Antitoxin consists of these free receptors 
floating in the blood serum. If now we introduce a liquid containing , 
the toxin into the blood, it is immediately neutralized by combin- 
ing with the free receptors through its hapto- 
phore group. All the combining affinities of 
the toxin are thus satisfied or saturated, so that 
the toxin is no lono'er able to unite with the 
receptors still attached to the cell, and this 
poison is thus rendered harmless. 
It is of the greatest practical importance to 
know from what organs or tissues the receptors 
derive their origin. 
It is by no means a necessary corollary of 
the side chain theory, as is often supposed, 
that the receptors are found only in those organs upon which the 
poisonous efiects of a toxine are particularly manifested. On the 
contrary, Ehrlich and Morgenroth^^ believe that receptors capable of 
«Erhlich, P., & Morgenroth, J. : tVirkung und entstehung der aktiven stoffe im 
serum nach der seitenkettentheorie. Handbuch der pathogen mikroorganismen, 
W. Kolle and A. Wassermann, Jena, 1904. 
Fig. le.— Third stage; the re- 
ceptors beginning to leave 
the cell. 
continued stimulation causes 
a reproduction of receptors. 
antitoxin formation; a 
fo.rmmolecule anchored 
to a receptor. 
