Life of Elie Metchnikoff, 1845-1916

by Olga Metchnikoff

This series of calamities depressed Metchnikoff, his old cardiac trouble returned, and he again became a prey to insomnia. We spent part of the holidays in the mountains, thinking it might do him good, but he did not care for a prolonged rest; he was preoccupied by the thought of his interrupted experiments and only thought of returning to the laboratory.

In 1898, he had some disquieting symptoms of kidney trouble, a little albumen. He consulted the celebrated German physician, von Noorden, who found nothing serious, but this did not reassure him and he continued to worry about himself.

Already some time previously, theoretical considerations on senile atrophies had directed his thoughts towards old age. His reflections now turned towards the psychological aspect of the problem; he analysed his personal sensations and realised that he, at the age of 53, felt an ardent desire to live. This imperious instinct for life, in spite of the inevitable evolution towards personal death and old age, brought his thoughts back to the disharmonies of human nature. But now, through all his gloomy reflections, he was borne up by the unshakable conviction that Science would succeed in correcting those disharmonies and he continued to work with untiring energy.

He had prescribed for himself a hygienic diet, based on the idea that the cause of his own condition and senility in general was due to a chronic poisoning by intestinal microbes. This diet consisted in avoiding raw food in order not to introduce noxious microbes into the intestines, and in absorbing their useful enemies, the acid-forming microbes of sour milk. This diet was very favourable to his health.

After he had finished his book on immunity he at last allowed himself to pass on to the new questions which preoccupied him, i.e. senility and death.

He set forth a sketch of his ideas in 1901 in a paper which he read at Manchester (Wilde Lecture) on the “Flora of the Human Body.” He reviewed this flora and pointed out the harmful effect of the microbes, especially those of the large intestine the toxins of which effect a chronic poisoning of the cells of our organism and thus provoke their gradual weakening. He then indicated the means of combating this evil, on the one hand by stimulating the vital activity of the cells exposed to enfeeblement, by means, for instance, of small doses of specific cytotoxins, and, on the other hand, by direct action on intestinal microbes. He concluded by saying that “the intestinal flora is the principal cause of the too short duration of our life, which flickers out before having reached its goal. Human conscience has succeeded in making this injustice obvious; Science must now set to work to correct it. It will succeed in doing so, and it is to be hoped that the opening century will witness the solution of this great problem.”

Metchnikoff considered that our chronic poisoning by intestinal microbes weakens our cellular elements; he supposed that the same cause might provoke senile phenomena, manifestly due to weakness of the tissues.

One of the first manifestations of senility being the whitening of hair, he began to study the mechanism of that. He had previously observed the dominant part played by phagocytosis in all phenomena of atrophy, and it occurred to him that it may be phagocytes which destroy the colouring matter of hair, a substance which, in the form of tiny granules, is enclosed within the hair cells. In fact, he found that the whitening process is accompanied by a stimulation of the amœboid cells which introduce their protoplasmic prolongations into the periphery of the hair. They absorb the coloured granules, or pigment, and digest it, partly on the spot, partly after carrying it into the root of the hair, often even in the connective tissue which supports the hairy scalp. As the pigment becomes destroyed, the hair loses its colour and whitens. The cells which devour the pigment—pigmentophages—belong to the category of macrophages which, in general, absorb all the enfeebled cells in the organism.

Metchnikoff was able to note similar phenomena in divers other senile atrophies either by his own ulterior researches or by collaboration with his pupils (MM. Salimbeni and Weinberg).

In the same way that the whitening of the hair depends on the destruction of pigment by pigmentophages, the wrinkles of the skin, weakness of the muscles, friability of the bones, and senile degenerescence of divers organs are caused by the destruction of weakened cells which do not defend themselves and thus become the prey of the stronger and more resisting macrophages. Senility is thus no other than a generalised atrophy. What is it that provokes it? The answer is: The swarming microbes in our large intestine. They form the permanent source of a slow poisoning of our organism. This fact alone suffices to explain one of the principal causes of the enfeebling of our tissues. It is not simultaneous in all the cells because of their different powers of resistance. The struggle and destruction of the weak by the strong is the cruel law of nature; therefore the macrophages, more resisting to poisons, take advantage of the weakening of other cells in order to devour them, and this is one of the causes of senility.