Annual Address by the President. 
17 
structive to that species. In this way an animal could be rendered 
artificially immune to this particular organism. It was also pointed 
out that a difference was present in the serum, according as the toxins 
alone or bacteria (living or dead) were used; injections of the latter 
(bacteria) giving to the serum a bacteriolytic power only, whereas in- 
jections of the former (toxins) make it both bacteriolytic and antitoxic. 
From which it was argued that at least two substances are produced, 
possessing, respectively, bacteriolytic and antitoxic properties. It was 
to elucidate the nature of these substances that Ehrlich advanced his 
theory. He taught that certain cells possessed lateral chains or receptors 
(like the loosely combined atom of H in the benzene ring), which are 
necessary to the nutrition of the cell on account of their affinities for 
albuminous substances, (Fig. 1, R.) By means of these receptors the 
protoplasm was able to enter into combination with albuminous sub- 
stances circulating in the blood and necessary for normal metabolic 
processes. He argued that these receptors were just as likely to enter 
into combination with the molecules of the toxin, which then worked 
destruction on the cell. 
Further, each protoplasmic molecule is capable of forming a great 
number of side chains, and a separate chain for each poison. Also each 
receptor is capable of anchoring one single body whatever its nature — 
albumin, peptone, or toxic (Barlow). How it is found that the bodies 
to be anchored consist of two groups possessing different affinities. The 
one group contains molecules capable of combining with the receptor, 
which combination fixes the toxin group firmly to the protoplasm, al- 
lowing the other group to exert its poisonous influence on the cell. The 
gi;oup that fixes the toxin molecule to the receptor is called the “hapto- 
phore,” and the other the “toxphore.” (Fig. 1, H and T.) 
If the toxophoric group is very poisonous, the cell is destroyed en- 
tirely, but if the cell is slightly damaged it seeks to repair the defect 
by the formation of fresh receptors. If these receptors are formed in 
great excess, they are shed and pass into, the general circulation. They 
form the “antitoxin/' (Fig. 2.) By this theory it is easily under- 
stood how a person may become immune. 
The toxin molecule that gains access to the blood may be unable to 
enter into combination with the cell, for two reasons, (1) the blood 
may be full of antitoxin, i. e., a vast number of free receptors may be 
present, on which the haptophoric group seizes, thus fixing the toxo- 
phore, which is then unable to come into contact with the protoplasm 
of the tissue cells (Fig. 2), or (2) there may be no fixed receptors of 
a suitable shape for the haptophore to combine with, in which event the 
toxin, being unable to find a suitable soil, is excreted by the kidneys. 
