12 
According to the former it is the physical movements of the ame- 
boid cell searching for food which, by a process known as phagoc}"tosis, 
takes the bacteria into its protoplasm, forms a digestive vacuole 
around it, and then excretes the enzymelike substances (cytase^) use- 
ful in protecting the organism against the soluble poison of the 
bacteria. 
According to Ehrlich the hungry protoplasm of any cell, with its 
complicated molecule having side chains of various combining affini- 
ties ready to unite with suitable food molecules brought to it by the 
blood and body juices, lies at the foundation of his explanation of the 
chemical production of the antitoxin. It is strange that the same 
combining affinity should exist between the protoplasm of the cell and 
the proteid molecules that furnish it food as between the cell proto- 
plasm and the toxines^ of the bacterial poisons. 
In considering Ehrlich's^ side-chain theory it is necessary to disre- 
gard the microscopic structure of the cell and to think of the proto- 
plasm as consisting of living molecules of extraordinary chemical 
complexit3^ The molecule of protoplasm has a central ‘Amcleus’’ 
with ‘’side chains,'- ** lateral chains.'' or ‘"bonds" of varying combin- 
ing capacities. These ‘'side chains" serve to bind the molecule to 
other molecules having proper combining affinities. 
This arrangement of molecules with side chains is a well-known 
occurrence in organic compounds. The benzol ring forms one of the 
best and simplest examples. 
H 
(OH) 
(OH) 
c 
C 
C 
/ \ 
/ \ 
/ \ 
HC CH 
HC CH 
HC C (OH) 
1 II 
i II 
i II 
HC CH 
HC C (CH3) 
HC C (OH) 
\ / 
\ / 
S / 
C 
C 
C 
H 
H 
H 
Benzol CgHg 
Metacresol CgH^ (CH3) (OH) 
Pyrogallic acid CgHg (OH) 
« ]\Iacrocytase, microcytase, philocytase. 
^ I have made a distinction in this bulletin between “ toxine” and toxin.’’ 
Some confusion arises in the literature for want of two words to represent two 
separate substances. The diphtheria poison contained in the toxic broth was first 
called “toxine,” usually “toxin.” It is now often spoken of as the “diphtheria 
poison.” This filtered broth, containing a number of poisonous substances, I have 
called the toxine. 
I have restricted the name toxin ” to the most important constituent of the 
toxine. The toxin, as will be found later, is only one of several allied poisons found 
in the toxine. 
c Ehrlich : Die wertbemessung des diphtherieheilserums und deren theoretische 
grundlagen. Klin, jahrb., Jena, v. 6 (2), 1897, pp. 299-326. 
