THEORIES OF IMMUNITY 
121 
concerned in other types, more especially in association with the 
parasitic types of bacteria. (See p. 132.) 
A. The Humoral Side-chain or Ehrlich Theory of Immunity.^ — 
According to Khrlich's conception, every cell of the body has two 
functions: a physiological function, which constitutes a special type 
of activity of the cell — secretion for a glandular cell, contraction for 
a muscle cell, or conduction for a nerve cell— and a nutritional func- 
tion, which is concerned with the removal of the necessary food sub- 
FiG. 6. — Side-chains, second order (agglutinins and precipitins). 1, side-chain attached 
to cell; c, haptophore group; b, zymophore group (agglutinophore or precipitinophore 
group) ; 2, side-chain to which is attached a bacteria cell ; a, haptophore group of bac- 
terial cell; 3, a cast-off side-chain of the second order, agglutinin or precipitin; 4, a side- 
chain attached to a bacterial cell (agglutination); 5, a bacterial cell; a, haptophore 
group; 6, an agglutinoid; the zymophore group is destroyed, leaving the haptophore 
group intact. 
stances from the general supply circulating in the blood or lymph 
channels, and the appropriation and eventual utilization of these 
specific food materials by the cell. These nutritional substances 
undoubtedly serve two purposes: Structural, to replace cellular waste, 
and fuel to supply cellular energy. 
The nutritional requirements of the individual cell are varied as 
their activities are varied , and Ehrlich conceives that each cell possesses 
1 See Aschoff: Ztschr. f. allgem. Path., 1902, vol. 
of the Ehrlich side-chain theorj'. 
1, No. 3, for a concise statement 
