GENERAL BACTERIOLOGY 
69 
cernecl in receiving food particles; for the latter pur¬ 
pose it is conceived that each cell possesses chemical 
affinities or as Ehrlich calls them “side chains,” which 
are the means of attracting to the cell the various nutri¬ 
tive substances. 
The poisonous material, such as products of bacteria, 
may also become attached to the body cell through its 
side chains, and, in this manner, injure the cell (Fig. 9). 
If the poison is severe enough the body cell so injured 
will die; if not, it will only be damaged; since the body 
cell must have food, and since its side chains are not 
I I 
o o 
Fig. 10.—Side-chains, with bacterial poison attached, cast off free into 
circulation, a, body cell; b, receptor or immune body (side-chain); c and d, 
bacterial poison. 
useful any more (having combined with the bacterial 
poisons), these side chains with the bacterial poisons 
attached to them, will be cast off into the blood stream, 
and new side chains will be formed (Fig. 10). But 
when new side chains are produced, not only enough 
are formed to replace the old ones, but many more 
than are really necessary, according to Weigert’s law 
of overproduction or overcompensation—if, for ex¬ 
ample, only six side chains have combined with bac¬ 
terial poison, and, having become useless to the body 
cell, were cast off, then, when regeneration of side 
