GENERAL BACTERIOLOGY 
55 
glands; such separable poison is given off by the bac¬ 
terium into the surrounding culture medium if it is 
grown artificially or into the circulation if it lodged 
in the body. For example, if bacteria are grown in 
liquid culture, such as broth, and this broth is filtered, 
it will be found that, although the bacteria will be left 
on the filter, the liquid substance, which had filtered 
through, although free from bacteria, will be found 
to be just as poisonous as the original broth in which 
the bacteria were grown. 
Very few bacteria produce such separable poisons, 
or exotoxins, the most important bacteria which belong 
to this class are the diphtheria, the tetanus, and the 
gas bacilli. 
2. Endotoxins (“internal” poisons) are inseparable 
poisons which are firmly attached, to the bacterial cell 
and are not secreted by it but are liberated only upon 
the death and disintegration of the bacterium. 
The greater number of the pathogenic bacteria pro¬ 
duce such poisons, the endotoxins; as, for example, the 
typhoid and the colon bacilli, the staphylococci and 
the streptococci, and the cholera spirilla, etc. 
3. In addition to these two classes of poisons, there 
is a third kind, present in all bacterial bodies, after 
the removal of exotoxins and endotoxins, a certain pro¬ 
tein residue, which differs from both of the above in 
that it is not specific (that is, whether it is derived 
from the diphtheria or the typhoid bacilli, it will pro¬ 
duce the same effects when injected into an animal) 
and in that its action is very mild, since its injection 
causes only mild local inflammations or abscesses. 
Besides the difference in the mode of production the 
exotoxins differ from the endotoxins in that the former 
are destroyed by lower temperature than the latter. 
Now that we know that the bacteria act not by their 
