The Biology of Senescence 



of animals decreases, like the companions of Odysseus of whom 

 Polyphemus ate a fixed number daily. 



The breakage rate of crockery or glasswear has sometimes 

 been used to illustrate the decline of a non-senescent population 

 (e.g. Medawar, 1952). A life-table for tumblers was actually 



100 



Fig. 7. — Survival curves of a German population. Hufeland's table ( 1 798) 



is based on 'experience' and estimates. Silbergleit's data are based on official 



statistics as given in the Deutschen Statistischen Jahrbuch for 1915. Both sets of 



data relate to N. Germany (From Vischer, 1947) 



constructed by Brown and Flood (1947) — that for annealed 

 tumblers approaches the curve of constant mortality, though 

 only roughly, while the decline of a smaller group of toughened 

 glass tumblers was nearly arith-linear (Fig. 8). Senescence, 

 however, does apparently occur in tumblers, since abrasions of 



22 



