S Biswas

Three mice in a cage, and each has her own schedule. One sniffs the bedding, another gnaws a grain, the third freezes by the water bottle. A month later, one of them will get an injection that temporarily stops her internal clock, while the other two continue living by the schedule.

An old mattress stops bouncing back: the filling clumps up, and the springs lose their resilience. The ovary changes with age in much the same way, except that instead of filling, stiff connective tissue grows inside it, and the role of springs is played by the cells that support the eggs.