If these facts are considered in the light of the known staining-reaction of the nuclein series, we must admit that the following conclusions are something more than mere possibilities. We may infer that the original chromosomes contain a high percentage of nucleic acid ; that their growth and loss of staining-power is due to a combination with a large amount of albuminous substance to form a lower member of the nuclein series, perhaps even a nucleoalbumin ; that their final diminution in size and resumption of stainingpower is caused by a giving up of the albumin constituent, restoring the nuclein to its original state as a preparation for division. The growth and diminished staining-capacity of the chromatin occurs during a period of intense constructive activity in the cytoplasm ; its diminution in bulk and resumption of staining-capacity coincides with the cessation of this activity. This result is in harmony with the observations of Schwarz and Zacharias on growing plant-cells, the percentage of nuclein in the nuclei of embryonic cells (meristem) being at first relatively large and diminishing as the cells increase in size. It agrees further with the fact that of all forms of nuclei those of the spermatozoa, in which growth is suspended, are richest in nucleic acid, and in this respect stand at the opposite extreme from the nuclei of the rapidly growing egg-cell.
Accurately determined facts in this direction are still too scanty to admit of a safe generalization. They are, however, enough to indicate the probability that chromatin may pass through a certain cycle in the life of the cell, the percentage of albumin increasing during the vegetative activity of the nucleus, decreasing in its reproductive phase. In other words, a combination of albumin with nuclein or nucleic acid is an accompaniment of constructive metabolism. As the cell prepares for division, the combination is dissolved and the nuclein-radicle or nucleic acid is handed on by division to the daughter-cells. It is a tempting hypothesis, suggested to me by Mr. A. P. Mathews on the basis of Kossel's work, that the nuclein is in a chemical sense the formative centre of the cell, attracting to it the foodmatters, entering into loose combination with them, and giving them off to the cytoplasm in an elaborated form. Could this be established, we should have a clue to the nuclear control of the cell through the process of synthetic metabolism. Claude Bernard advanced a nearly similar hypothesis twenty years ago ('78), maintaining that the cytoplasm is the seat of destructive metabolism, the nucleus the organ of constructive metabolism and organic synthesis, and insisting that the role of the nucleus in nutrition gives the key to its significance as the organ of development, regeneration, and inheritance.' That the nucleus is especially concerned in synthetic metabolism is now becoming more and more clearly recognized by physiological chemists. Kossel concludes that the formation of new organic matter is dependent on the and that nuclein in some manner plays a leading role in this process ; and he makes some interesting suggestions regarding the synthesis of complex organic matters in the living cell with nuclein as a starting-point. Chittenden, too, in a review of recent chemico-physiological discoveries regarding the cell, concludes : "The cell-nucleus may be looked upon as in some manner standing in close relation to those processes which have to do with the formation of organic substances. Whatever other functions it may possess, it evidently, through the inherent qualities of the bodies entering into its composition, has a controlling power over the metabolic processes in the cell, modifying and regulating the nutritional changes" ('94).