ARTICLES 419 



insects proceeds without interruption, each species having its 

 own separate time ; the colonies of wasps, for instance, do 

 not die off annually, leaving only the queens, as in cold cli- 

 mates ; but the succession of generations and colonies goes 

 on incessantly. It is never either spring, summer, or autumn, 

 but each day is a combination of all three." 



The age-cycle, with its sequence of birth, growth, maturity, 

 decay, and death, is the most typical and most inevitable 

 phenomenon in Nature. It is not only the normal sequence 

 in the organism as a whole, but the phenomena of senescence 

 and rejuvenescence are continually being repeated within the 

 organism. These internal periodicities are of essentially the 

 same character as the age-cycle of the organism, except as 

 regards the time factor. " In cells," says Child, 1 " where 

 function is accompanied by extensive accumulation and dis- 

 charge of substances, such, for example, as the gland cells, 

 storage cells, etc., the cycles of activity and morphological 

 change are essentially age-cycles — that is to say, the period 

 of loading of the cell is a period of decreasing metabolic activity, 

 of senescence, and the period of discharge one of increasing 

 activity, of rejuvenescence, which makes possible a repetition 

 of the cycle." In the pancreas of the toad, for example, the 

 cells, when ready to secrete, are loaded with granules, and in 

 this condition are only very slightly active metabolically. As 

 the cell secretion is discharged, the granules gradually dis- 

 appear to a point when they are practically absent. In this 

 condition, the cell is again capable of a high rate of metabolic 

 activity ; if nutrition is present, the process of loading occurs 

 once more. This cycle of changes, which may occur within a 

 few hours, and which may be repeated within a single cell, 

 Child believes, is not fundamentally different from the age- 

 cycle of organisms. It exhibits all the essential features, up 

 to a certain point, of senescence and rejuvenescence. The 

 cell undergoes changes similar to those of the age-cycle, though 

 their period is short. At the same time, as Child says, the 

 gland cell may be undergoing senescence in the stricter sense 

 — that is to say, changes in the more stable framework of the 

 protoplasm may be occurring which are not wholly compen- 

 sated by the functional cycle. 



According to Benjamin Moore, 3 the living cell may be 

 regarded, from the physico-chemical point of view, as a pecu- 

 liar energy transformer : chemical energy in the living cell 

 being converted by the colloidal structure into biotic energy, 



1 Child, C. M., Senescence and Rejuvenescence . (University of Chicago Press, 



I9I5-) 



3 Benjamin Moore, The Origin and Nature of Life . (London: Williams and 

 Norgate, 191 2.) 



