oplasm, both by solution
and by ionization of such substances as undergo electric dissociation; and
serves to regulate the temperature of the protoplasmic mass. Furthermore,
in organic tissues, most of the important chemical reactions of the
protoplasm are reversible hydrolyses; i.e., water actually enters into the
reaction or is liberated by it, and the equilibrium point of the reaction
is changed by the proportions of water which are present in the reacting
mass. Hence, the presence of large proportions of water in the colloidal
complex known as protoplasm has a very important influence upon its
possibilities of biological reactions.

SALTS

Active protoplasm contains mineral salts in solution. These are of the same
general nature as those found in sea-water, which is the original habitat
of the earlier evolutionary forms of living matter. Or, it might be said
that both plants and sea-water derive their mineral salts from the same
source, namely the soluble salts of the soil. Recent investigations have
shown that the proportions of sodium ions to calcium ions in sea-water are
precisely those which maintain fats, proteins, etc., in a true colloidal
emulsion; and that comparatively small variations in the ratio of these two
cations produce very marked effects upon the colloidal conditions of these
substances in an artificial colloidal preparation, which resemble very
closely the changes which apparently take place in cell protoplasm under
the influence of narcotics, or nerve stimulants, in blood-coagulation, in
the parthogenetic development of germ cells, in cancerous growth of
tissues, etc. In other words, in so far as it has been studied in this
respect, cell plasma exhibits exactly the same responses to variations in
the proportions of salts (electrolytes) in solution, that artificial
emulsions of oils (fats) in water do; and the normal, or critical,
equilibrium proportion of these electrolytes for all colloidal complexes is
that in which they occur in sea-water. It must be admitted that there is as
yet no definite evidence that the observations which have been made upon
the protoplasm of animal tissues will apply equally well to plant cell
protoplasm. But many of the phenomena which have been studied in animal
tissues have what are apparently similar, if not identical, effects in
plant tissues, and it seems reasonable to suppose that these conclusions
apply generally to protoplas