and
Medicine," 463 pages, 54 figs., New York, 1919.

BURTON, E. F.--"The Physical Properties of Colloidal Solutions," 200 pages,
18 figs., London, 1916.

CASSUTO, L.--"Der Kolloide Zustand der Materie," 252 pages, 18 figs.,
Dresden and Leipzig, 1913.

LIESEGANG, R. E.--"Beitraege zu einer Kolloidchemie des Lebens," 144 pages,
Dresden, 1909.

OSTWALD, W., trans. by FISCHER, M. H.--"Theoretical and Applied Colloid
Chemistry," 218 pages, 43 figs., New York, 1911.

OSTWALD, W., trans. by FISCHER, M. H.--"A Handbook of Colloid-Chemistry,"
278 pages, 60 figs., Philadelphia, 1915.

TAYLOR, W. W.--"The Chemistry of Colloids," 328 pages, 22 figs., New York,
1915.

ZIGMONDY, R., trans. by ALEXANDER, J.--"Colloids and the Ultramicroscope,"
238 pages, 2 plates, New York, 1909.

ZIGMONDY, R., trans. by SPEAR, E. B.--"The Chemistry of Colloids," 274
pages, 39 figs., New York, 1917.

CHAPTER XVI

THE PHYSICAL CHEMISTRY OF PROTOPLASM

Thus far, we have considered the chemical nature of the various groups of
compounds which are found in the tissues of living organisms, laying
emphasis upon those which are of plant origin. These compounds constitute
the material, or machinery, of the cell, and their various transformations
furnish the energy for its operation. We come now to a study of the mode of
its operation, or the processes of vital phenomena.

Our knowledge of these matters is not yet far enough advanced to permit a
definite statement as to whether there is any difference between the
protoplasm of plant tissues and that of animal origin in their modes of
action, or in the physical-chemical changes which constitute the vital
phenomena in the two groups of living organisms. Thus far, no such
differences have been discovered. Hence, in the following discussions, no
attempt is made to differentiate between animal and plant protoplasm. Most
of the facts and principles which are here presented have been developed as
the result of the study of the physiological chemistry of animal life. No
similar careful study of plant chemistry has yet been carried out; but
preliminary studies seem to indicate that the same general principles apply
to all protoplasm, regardless of whether it is of plant or of animal
origin. It is possible, of course, that further studies of plant protoplasm
will render necessary some modifications of some of these views as applied
to the growth o