Disease, frequent, constant, and inevitable as it is, is, however, nothing but a fact outside the natural order. Its character is clearly accidental, and it interrupts the normal cycle of evolution. Medical observation teaches us, on the other hand, that the health of the body reacts on that of the mind; and therefore man as a whole, moral and physical, is affected by disease. Bacon described a diseased body as a jailer to the soul, and the healthy body as a host. Pascal recognized in diseases a principle of error. “They spoil our judgment and our senses.”
I am not expressing a chimerical hope when I predict that science will conquer disease. Medicine has at last issued from the contemplative attitude of so many centuries; it has engaged in the struggle, and signs of victory are already appearing. Disease is no longer the mysterious power which it was impossible to escape. Pasteur gave to it a body. The microbe can be caught. In the words of Schopenhauer, an alteration of the atmosphere so slight that it is impossible to detect it by chemical analysis may bring on cholera, yellow fever, the black plague, diseases which carry off thousands of men; and a slightly greater alteration might endanger all life. The at once mysterious and terrifying spectacle of the cholera at Berlin in 1831 had such an effect on the philosopher that he fled in terror to Frankfort. It has been said that this was the origin of his pessimism, and that but for this he would have continued to teach idealistic philosophy in some Prussian university. L. Hartmann, another celebrated leader of contemporary pessimism, has also said that disease will always be beyond the resources of medicine. Facts have given the lie to these sombre prognostics. The microbic origin of most infectious diseases has been recognized. The discovery of attenuated poisons and serums has diminished their gravity. An exact knowledge of methods of contagion has enabled us to erect against them impregnable barriers. Cholera, yellow fever, the plague knock in vain at our doors. Diphtheria, dreaded by every mother, has partially lost its deadly character. Puerperal fever and blindness of the new-born child are tending to disappear. Legend tells us that Buddha in his youth, frightened at the sight of a sick man, expressed in his father’s presence the wish to be always in perfect health and sheltered from disease. The King answered: “My son! you are asking the impossible.” But it is towards the realization of this impossibility that we are on our way. Science is repelling the attacks of disease.
§ 2. Old Age.
Old age is another sorrow of humanity. The stage of existence in which the strength grows less and never grows greater, and in which a thousand infirmities appear, is not, however, a stage universal in animals. Most of them die without our perceiving in them any apparent signs of senile weakness. On the other hand, some vegetables exhibit these signs. Some trees are old; but it is in birds and mammals that this decay, with the train of evils which accompanies it, becomes a very marked phase of existence. In man to debility is added a bodily shrinkage, grey hairs, withered skin, and the wearing out and loss of teeth. The exhausted and atrophied organism offers a favourable field to all intercurrent diseases and to every cause of destruction. It is this discrepitude which makes old age so hateful. All desire to be old, said Cicero; and when they are old, they say that old age has come quicker than they expected. La Bruyère expresses it in an apothegm, “We want to grow old, and we fear old age.” One would like longevity without old age.
But can life be prolonged without senility diminishing its value? Metchnikoff thinks it can. He more or less clearly catches a glimpse of a normal evolution of existence which would make it longer and nevertheless exempt from senile decay.
It is remarkable that we have so few scientific data on the old age of man, and we have still fewer on that of animals. The biologist knows no more than the layman. The old age of the dog is betrayed by its gait. Its coat loses its lustre, just as in disease. The hair whitens around the forehead and the muzzle. The teeth grow blunt and drop out. The character loses its gaiety and becomes gloomy; the animal becomes indifferent. He ceases to bark, and often becomes blind and deaf.
It is admitted that senile degeneration is due to an alteration affecting most of the tissues. The cells, the special anatomical elements of the liver, the kidney, and the brain are reduced by atrophy and degeneration. At the same time, the conjunctive woof which serves them as a support develops, on the contrary, at the expense in a measure of the higher elements. For this reason the tissues harden. We know that the flesh of old animals is tough. We know in pathology that this is happening to the tissues. It is due to growth, to injury to the active and important elements, to the elements of support of the organs. They form a tissue sometimes called packed tissue, to show its secondary rôle with reference to the elements which are deposited in it. This kind of degeneration of the organs is known as sclerosis. It constitutes the characteristic lesion of a certain number of chronic diseases; and these diseases are serious, for the stifling of the characteristic elements by the less important elements of the conjunctive or packed tissue results in the more or less complete reduction or suppression of the function.
The blood vessels also undergo this transformation, and what we may call universal trouble and danger ensue. This sclerosis of the arteries, this arterio-sclerosis, not only deprives the walls of the blood vessels of the suppleness and elasticity which are necessary for the proper irrigation of the organs, but it makes them more fragile. Thus it becomes a cause of hemorrhage, which is a very serious matter as far as the brain and lungs are concerned.
It is remarkable that the alteration of the tissues during old age should be exactly similar to this. This is inferred from the few researches that have been made on the subject—from those of Demange in 1886, of Merkel in 1891, and finally from the researches of Metchnikoff himself. It is a generalized sclerosis. As its consequence we have the lowering of the proper activity of the organs and the danger of cerebral hemorrhage created by arterio-sclerosis. The transformations of the tissues in old men are therefore summed up in the atrophy of the important and specific elements of the tissues, and their replacement by the hypertrophied conjunctive tissue. This sclerosis is comparable to that of chronic diseases; it is a pathological condition. Thus old age, as we understand it, is a chronic disease and not a normal phase of the vital cycle.
On the other hand, if we ask ourselves what is the origin of the scleroses which engender chronic diseases, we find that they are due to the action of various poisons, among which syphilitic poison and the immoderate use of alcohol take the first place. These are also the usual causes of senile degeneration. But there must be some other, some very general cause to explain the universality of the process of senescence. Metchnikoff thinks that he has found this cause in the microbes which swarm in man’s digestive tube, particularly in the large intestine. Their number is enormous. Strassburger has given an approximate calculation, but words fail to express it. We have to imagine a figure followed by fifteen zeros. This microbic flora is composed of “bacilli” and of “cocci,” and comprises a third of the rejected matter. It produces slow poisons, which, being at once reabsorbed, pass into the blood and provoke the constant irritation from which results arterio-sclerosis and the universal sclerosis of old age. Instead of enjoying a healthy and normal old age, in which the faculties of ripening years are preserved, we drag out a diminished life, a kind of chronic disease, which is ordinary old age. This is due, according to Metchnikoff, to the parasitism and the symbiosis of microbic flora, lodged in a part of the economy in which it finds all the conditions favourable to its prolific expansion. Such is the specious theory, held to the verge of intrepidity, by which this investigator explains the misery of our old age, and which inspires him with the idea of a remedy. For his observations conclude with a régime, a series of prescriptions by which the author fancies that life may be lengthened and the evils of old age swept from our path. The dangerous flora must be transformed into a cultivated and selected flora. Although the organ in question may be of doubtful utility, and although its existence, the legacy of atavic heredity, must be considered as a disharmony of human nature, Metchnikoff does not go so far as to propose that it should be cut away, and that we should call in surgery to assist in making mankind perfect! But the rational means he proposes will be endorsed by the most judicious students of hygiene; and their effect, if it is not as wonderful as one hopes for, cannot fail to ameliorate the conditions of old age and make it more vigorous.