not too much to say that the differences between the
chemical phenomena which are called "vital" and those which take place in
ordinary laboratory reactions are due to the fact that the former are
manifestations of the interchanges of energy between the different phases
of a heterogeneous colloidal system, while the latter are governed by the
laws of ordinary stoichiometric combinations.

ELECTRICAL PHENOMENA OF PROTOPLASM

The investigations of this phase of the physical chemistry of protoplasm
have dealt almost exclusively with animal tissues and reactions, and have
included the study of such phenomena as nerve impulses, muscular
contractions, heart-beats, glandular secretions, etc. Tissues which respond
to nerve, or brain, control are, of course, not found in plants. But there
is plenty of experimental evidence to show that plant protoplasm carries
electrical charges and exhibits electrical phenomena which are similar in
character to those of animal tissues. In fact, it has been shown that the
contraction of the lobes of the Venus' fly trap, when they close over an
imprisoned insect, are accompanied by electrical phenomena in the leaf
tissues which are precisely similar to those which take place in an animal
muscle when it contracts. It seems probable that many of the observations
and conclusions which have been derived from the study of the electrical
disturbances in animal tissues may later be found to have definite
applications to the vital phenomena of plant cells. Hence, it seems proper
to give some brief consideration to these matters here.

The statement has been made that "every active living cell is essentially
an electric battery," and it is believed that every activity of living
matter, such as the rhythmic contraction of the heart, the passage of a
nerve impulse, etc., is accompanied by an electric disturbance in the
protoplasm of the tissues in question. Experimental proof of this
electrical disturbance has been repeatedly obtained, by connecting a
delicate galvanometer in a circuit through the living tissue which is
undergoing different activities and obtaining widely varying readings of
the instrument as the different phenomena are in progress, or by connecting
the instrument with muscular tissue and observing its fluctuations with
either the irregular contractions of a voluntary muscle or with the
rhythmic contractions of a heart muscle.

By means of such investigations as thos