Aristotle On Youth and Old Age,On Life and Death,On Breathing-Part 23

To be born and to die are common to all animals, but there arespecifically diverse ways in which these phenomena occur; ofdestruction there are different types, though yet something iscommon to them all. There is violent death and again natural death,and the former occurs when the cause of death is external, thelatter when it is internal, and involved from the beginning in theconstitution of the organ, and not an affection derived from a foreignsource. In the case of plants the name given to this is withering,in animals senility. Death and decay pertain to all things that arenot imperfectly developed; to the imperfect also they may beascribed in nearly the same but not an identical sense. Under theimperfect I class eggs and seeds of plants as they are before the rootappears.It is always to some lack of heat that death is due, and inperfect creatures the cause is its failure in the organ containing thesource of the creature's essential nature. This member is situate,as has been said, at the junction of the upper and lower parts; inplants it is intermediate between the root and the stem, insanguineous animals it is the heart, and in those that are bloodlessthe corresponding part of their body. But some of these animals havepotentially many sources of life, though in actuality they possessonly one. This is why some insects live when divided, and why, evenamong sanguineous animals, all whose vitality is not intense livefor a long time after the heart has been removed. Tortoises, forexample, do so and make movements with their feet, so long as theshell is left, a fact to be explained by the natural inferiority oftheir constitution, as it is in insects also.The source of life is lost to its possessors when the heat withwhich it is bound up is no longer tempered by cooling, for, as Ihave often remarked, it is consumed by itself. Hence when, owing tolapse of time, the lung in the one class and the gills in the otherget dried up, these organs become hard and earthy and incapable ofmovement, and cannot be expanded or contracted. Finally things come toa climax, and the fire goes out from exhaustion.Hence a small disturbance will speedily cause death in old age.Little heat remains, for the most of it has been breathed away inthe long period of life preceding, and hence any increase of strain onthe organ quickly causes extinction. It is just as though the heartcontained a tiny feeble flame which the slightest movement puts out.Hence in old age death is painless, for no violent disturbance isrequired to cause death, and there is an entire absence of feelingwhen the soul's connexion is severed. All diseases which harden thelung by forming tumours or waste residues, or by excess of morbidheat, as happens in fevers, accelerate the breathing owing to theinability of the lung to move far either upwards or downwards.Finally, when motion is no longer possible, the breath is given outand death ensues.