The other class of toxic substances, called endotoxines, are not secretion products, but are contained in the bacterial substance and become active by the destruction and disintegration of the bacteria.

They can be artificially produced by grinding up masses of bacteria, and in the body the destruction and solution of bacteria which is constantly taking place sets them free.

The toxines and the endotoxines are of an albuminous nature, and act only when they come in contact with the living cells within the body.

When taken into the alimentary canal they are either not absorbed or so changed by the digestive fluids as to be innocuous.

Many of the ordinary food substances, even a material apparently so simple as the white of an egg, are highly injurious if they reach the tissues in an unchanged form.
By means of these substances the bacteria produce such changes in their environment within the body that this becomes adapted to their parasitic existence.