In the case of poisons the capacity of the cell for adaptation to unusual conditions is of great importance.
It is probable that certain changes take place within the cells, owing to which the function can be continued in spite of the unusual conditions which the presence of the poison brings about.

It is in this way that the habitual use of such poisons as morphine, alcohol and tobacco, to speak only of those best known, is tolerated.

The cell life can become so accustomed to the presence of poisons that the cell activities may suffer in their absence.
_Repair_ of the injuries which the body receives is effected in a variety of ways.

We do not know how intracellular repair takes place, but most probably the cells get rid of the injured areas either by ejecting them, or chemical changes are produced in the altered cell substance breaking up and recombining the molecules.

When single cells are destroyed, the loss is made good by new formation of cells, the cell loss stimulating the formative activity of the cells in the vicinity.