The Prolongation of Life: Optimistic Studies

by Elie Metchnikoff

Theory of the immortality of unicellular organisms—Examples of very old trees—Examples of short-lived plants—Prolongation of the life of some plants—Theory of the natural death of plants by exhaustion—Death of plants from auto-intoxication

It must surprise my readers to find how little science really knows about death. Although death has a preponderating place in religions, systems of philosophy, literature and folk-lore, scientific works pay little attention to it. This unfortunate fact explains, although it may not justify, the bitter attack made on science on the grounds that it is occupied with minutiæ and neglects the great problems of human life, such as death. When Tolstoi was absorbed by the problem and searched for some solution in the writings of scientific men, he found that the explanations were trivial or inexact. In consequence he was extremely indignant with the men who devoted themselves to the investigation of what seemed to him useless problems (such as the insect world, or the structure of cells and tissues) and who were yet unable to say what the destiny of man or death might be.

I am far from claiming to solve these problems; I can do little more than describe the actual state of the question of natural death. I hope in this way at least to prepare for scientific investigation, and to call attention to it as the most important problem of humanity.

By the use of the phrase “natural death” I mean to denote a phenomenon that is intrinsic in the nature of an organism and that is not the mere result of an external accident. Popular phraseology includes under natural death all cases due to diseases. But as such deaths can be avoided and are not due to qualities inherent in the organism, it is erroneous to include them in the category “natural death.”

In nature, death comes so frequently by accident that there is justification for asking if natural death really occurs. It used to be thought that death was the inevitable end of life and that the living principle contained within itself the germ of death. Accordingly, it was a surprising discovery that many low organisms die only by accident, and that if such accident be avoided, death does not fall on them. Unicellular organisms (such as infusoria, many other protozoa and low plants) multiply by simple division, the organism thus giving rise to two new organisms; the parent so to speak loses itself in its offspring without undergoing death. To criticisms of this mode of presentment of the facts, Weismann, who has attracted most attention to the view, replied as follows:—“In cultures of Infusoria, these little animals continually multiply by division and no dead bodies are found. The individual life is short, but it ends not in death but in transformation to two new individuals.”

Max Verworn,[71] a physiologist of repute, objected that Weismann had overlooked the occurrence within the organism of a process of partial destruction, and that under certain conditions a complete organ of the infusorian body (the nucleus) dies and is absorbed. Such death of a part, however, is not followed by death of the whole, and as the continuous destruction of some of the cells in our own bodies is not regarded as our death, the criticism of the German physiologist cannot be accepted.

It is not only the extremely short-lived microscopic organisms that escape death. Some of the higher plants, which may attain to gigantic size, encounter death only by accidents. There is nothing to be found in the nature of their organisation which would seem to indicate that death is the inevitable or even probable result of their constitutions.

The longevity of some trees has long been notorious, as these appear to live for many centuries and to die only when they are overwhelmed by the ravages of a storm or killed by human agency.

When the Canary Islands were discovered, in the beginning of the fifteenth century, the early explorers were struck with the gigantic size of a dragon tree which was venerated by the natives as their tutelary deity. The tree stood in a Garden at Orotava in Teneriffe, and even in these early days, its huge trunk contained a gigantic hollow. The tree did not reward the worship of the natives, who were annihilated by the Spaniards, and it survived them for nearly four centuries. At the end of the eighteenth century it was seen by Humboldt,[72] who found that the trunk was forty-five feet in circumference, and who attributed to it a great age because dragon trees grow extremely slowly. Early in the nineteenth century (1819) a furious tempest swept over Orotava and with a gigantic crash nearly a third of the crown of leaves and branches fell on the ground. Notwithstanding this shock, the monster survived for fifty years. Berthelot,[73] who visited it in 1839, described it as follows:—“A dragon tree stood in front of my dwelling, grotesque in form, gigantic in size, which a storm had smitten without overwhelming. Ten men would have much ado to girdle its vast trunk, fifty feet in circumference at the ground. The huge column had a deep cave within it, hollowed by the ages; a rustic porch gave access to the interior, and the lofty dome, although half had been destroyed by a storm, still bore an enormous crown of branches.”