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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 of plants; but they are believed to represent the best which is now known of the physical chemistry of the plant-cell activities.