126 j BACTERIOLOGY. 
weakened. Those remaining active are then further 
acted upon by the alexines in the tissues and by the 
substances given off by the leucocytes. If these pro- 
tective substances are insufficient the infection is estab- 
lished. RR. Pfeiffer’s experiments with cholera and 
typhoid cultures injected into the peritoneal cavity of 
the guinea-pig along with specific protective serum 
showed that the bacteria were altered and destroyed by 
the serum within a few minutes, just as if they had 
been non-virulent bacteria, and this without the assist- 
ance of the phagocytes. In this case non-virulent bac- 
teria die because they produce no lysines to destroy the 
alexines, while those which are virulent do not thrive, 
because although they produce lysines, the antilysines 
in the serum destroy them, being thus acted upon by 
alexines in like manner to the non-virulent bacteria. 
As to the development of the specific protective sub- 
stances, the most plausible theory seems to us to be that 
they are formed by the activity of the cells from the 
bacterial poisons, the lysines. These substances are 
stated by Pfeiffer and Marx to be most abundant in the 
spleen, lymphatic glands, and bone-marrow. 
Ehrlich and others believe antitoxin to be a portion 
of the substance of certain cells, which, having been 
stimulated by their effort to replace portions of their 
substances destroyed by previous doses of toxin, have 
reproduced it in excess. This cell substance, being 
free in the fluids of the body, combines with the toxin, 
and thus neutralizes it. But it is difficult by this 
theory to explain many known facts, such as the one 
that a fully neutralized mixture of toxin and antitoxin 
is still capable of producing in the body more anti- 
toxin. Others hold that the antitoxins, as the other 
