Further researches on the intestinal flora--_Forty Years' Search for
a Rational Conception of Life._
Since Metchnikoff had conceived the idea that a considerable part was
played in human life by the intestinal flora, his thoughts had centred
around a study which he thought profitable: that of the influence of
intestinal microbes on the normal and on the pathological organism.
So, on his return from Russia, he took advantage of the fact that an
epidemic of infantile cholera had broken out in order to continue his
former investigations of that disease. The numerous cases which he
thus studied allowed him finally to establish the specific part of the
_B. proteus_ as well as the similarity between infantile cholera and
Asiatic cholera. This time he succeeded in contaminating, not only
young anthropoid apes, but also new-born rabbits, and that not only
through sick children's excreta, but by pure cultures of the _proteus_,
which eliminated every doubt of the specificity of this microbe.
Metchnikoff explained the contamination of children exclusively
breast-fed, either by the presence of a carrier personally refractory,
among the entourage, or by the transport of dirt, by means of flies,
on the objects which infants so readily put into their mouths.
He therefore advised preventive means of absolute hygiene and
cleanliness, especially where suckling infants are concerned.
During the year 1912, he studied the intestinal flora and the influence
of divers food diets. He experimented upon the rat, an omnivorous
animal whose mode of feeding resembles that of man. The rats were
divided into three lots, of which one was kept to a meat diet, another
to a vegetarian régime, and the third to a mixture of both. The meat
diet was least favourable, and the best results obtained by the mixed
food.
These observations led Metchnikoff to the study of other problems
intimately connected with the same question.
He undertook a series of researches in collaboration with his pupils,
MM. Berthelot and Wollman, on the conditions which cause the diminution
within the organism of the toxic products of intestinal microbes. They
found that the quantity of these products was very small in those
animals which feed on vegetable or fruit containing much sugar, such
as carrots, beetroot, dates, etc. This is explained by the fact that
the products of the decomposition of sugar are acids which prevent the
development of putrefying microbes. But the sugar, rapidly absorbed by
the walls of the small intestine, only reaches the large intestine in a
much reduced quantity, for it is only up to a certain point during its
journey that the cellulose of vegetables, rich in sugar, protects that
substance. The question, therefore, was to find the means of making
it reach the large intestine in greater quantities. In the intestine
of a normal dog, an innocuous microbe was found, the _Glycobacter
peptonicus_, which decomposes starch into sugar.
Metchnikoff made some laboratory animals ingest this microbe together
with food, and ascertained that it reached the large intestine and
decomposed in it the starch of farinaceous food into sugar, of which
the acid products prevented the swarming of putrefying microbes. By
this process it is possible to reduce to a minimum and even sometimes
to eliminate the production of phenol and indol in rats subjected to a
mixed diet and made at the same time to ingest cultures of the lactic
bacillus and of the glycobacter.
Metchnikoff applied these different diets to himself and to other
individuals and obtained concordant results.
However, he ascertained that it is not only the food diet which
regulates the quantity of microbian poisons contained in the organism;
that quantity sometimes varies very much in spite of an identical
diet. He thought that a very important part of influence is due to
pre-existing microbes which prevent or favour the development of
microbes of putrefaction. All these questions, complicated by the
richness and variety of the intestinal flora, still demanded a long
series of laborious researches.
At the end of the winter he felt tired, and we went to the seaside
during the holidays. But the sharp sea air did not suit him; he had
a beginning of cardiac asthma and nearly fainted during a walk. We
therefore had to come away from the sea, and went inland, to Eu. At the
beginning of our stay, Metchnikoff did not feel well, walking tired
him, he suffered from cardiac intermittence; it was only gradually
that his condition improved and he was able to write the preface to a
Russian edition of his philosophical articles.
This book was entitled _Forty Years' Search for a Rational Conception
of Life_, and the articles record the evolution of his ideas and his
search "not only for a rational understanding of life, but also for the
solution of the problem of death, which is so full of contradictions."
This collection of articles enables us at the same time to follow the
gradual transition from the pessimism of his youth to the optimism of
his maturity. His first writings[28] relate to the discords of human
nature and the lack of a solid basis for morals.
[28] _Education from an Anthropological Point of View_, _The
Matrimonial Age_, _The Conception of Human Nature_, _The
Struggle for Existence in a General Sense_. See Bibliography.
But, already in 1883, he concluded an opening _Causerie_ at the
Naturalists' Congress in Odessa, by the following words: "The
theoretical study of natural history problems, in the widest sense of
the word, alone can give a sound method for the comprehension of truth
and lead to a definite conception of life--or at least to an approach
to it."
Another article, _The Curative Forces of the Organism_, sums up his
phagocyte theory, and states the fact that the organism possesses
special powers of struggle against enemy elements.
In 1891, he wrote _The Law of Life_, in which we find the dawning idea
that the lack of harmony in human structure does not make a happy
existence and a rational code of morals impossible. Morals must consist
"not in rules of conduct adapted to our present defective human nature,
but on conduct based upon human nature modified, according to the ideal
of human happiness."
_The Flora of the Human Body_, published in 1901, is a study in which
Metchnikoff's optimism assumes a definite form, for he speaks of the
efficacy of certain means of struggling with our lack of harmony.
The last chapter in the book, "A Conception of Life and of Medical
Science," introducing the word Orthobiosis, strikes the optimistic
chord, winged and conclusive, which must result from victory over the
disharmonies of human nature. This is Metchnikoff's ultimate formula,
summing up the problems of life and of morals:
The ethical problem reduces itself to this: to allow the majority of
human beings to reach life's goal, that is, to accomplish the whole
cycle of a rational existence to its natural end. We are still very
far from that. We can but sketch the rules to follow in order to
attain this ideal. Its final realisation will demand more scientific
researches, which must be allowed the widest and freest scope. It is
to be foreseen that existence will have to be modified in many ways.
Orthobiosis demands an active, healthy, and sober life, devoid of
luxury and excess.
We must therefore modify present customs and eliminate those extremes
of wealth and poverty which now bring us so many evils. As time goes
on, when Science has caused present evils to disappear, when men no
longer tremble for the life and welfare of their dear ones, when
individual life follows a normal course--then Man can attain a higher
level and more easily devote himself to exalted goals.
Then Art and pure Science will occupy the place which is due to them
and which they lack at the present moment in consequence of our many
cares. Let us hope that men will understand their true interests and
contribute to the progress of orthobiosis.
Many efforts are necessary, much self-sacrifice, but they will be
attenuated by the consciousness of an activity directed towards the
real goal of human existence.