. Senescence and rejuvenescence. Age; Reproduction. CONCLUSIONS FROM EXPERIMENTS 191 stable components of the protoplasm may be accumulating or undergoing changes which are not, or not wholly, compensated by the functional cycle. Other gland cells undergo very similar periodic changes in structure, the whole peripheral region being discharged bodily in some cases and the cell regenerating from a small basal portion. Many other cells in the organism not regarded as gland cells pass through somewhat similar cycles. Various cells, for example, accumulate reserves, such as starch in plants and fat
. Senescence and rejuvenescence. Age; Reproduction. CONCLUSIONS FROM EXPERIMENTS 191 stable components of the protoplasm may be accumulating or undergoing changes which are not, or not wholly, compensated by the functional cycle. Other gland cells undergo very similar periodic changes in structure, the whole peripheral region being discharged bodily in some cases and the cell regenerating from a small basal portion. Many other cells in the organism not regarded as gland cells pass through somewhat similar cycles. Various cells, for example, accumulate reserves, such as starch in plants and fat in animals and various other substances. As the loading of such cells pro-. FiG. 68.—Pancreas cells o£ toad almost completely discharged after prolonged stimulation. From preparations loaned by R. R. Bensley. ceeds, they approach quiescence, but when conditions change so that the previously accumulated substances are removed, they may undergo a rejuvenescence. Although we have at present little positive knowledge along this hne, it seems probable that various periodic changes in organisms or parts are of this general character. Quiescent periods following periods of abundant nutrition and accumulation of substance occur in the protozoa and other lower animals as well as in many plants, particularly in parts specialized as storage organs, such as bulbs, tubers, etc. It is a familiar fact that in certain tropical species of trees the loss of leaves, followed by a quiescent period, occurs at different times on different branches. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Child, Charles Manning, 1869-1954. Chicago, Ill. , The University of Chicago Press
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