As cat grows old its' reduces its' activity and adaptation abilities. The decrease of muscle mass leads to reduction of strength and resistibility of organism: cat becomes more sluggish and less quick. Compensation of liquid lost during vomiting or diarrhea happens much slower; heat regulation becomes less effective, so supercooling of organism may cause hypothermia (body temperature pull-down). Much longer lasts compensation of damaged tissues, and partial deterioration of smell, vision, hearing and taste occurs.
An old cat becomes less interested in things happening around, preferring to stay passive for long. It rejects changes in order and hardly accommodate to changes in diet and environment.
Kidney and tooth disorders often happen in old cats, as well as tumors. Some of them lose the ability to normal defecation; others are unable to control muscles and bladder, which leads to enuresis. Their skin loses elasticity, and since a cat less takes care of cleanness of its' body, ear and eye egesta may accumulate that its' master has to move away.
However one should not regard old age as a disease. It's just a state at which a cat, unfortunately, loses living force and an ability to accommodate itself to changes.
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).