Resistance (biology)

“ The resistance or want of resistance which the body opposes to its invaders is medically referred to as the predisposition to the disease. What the real conditions of this predisposition are, we do not know. Experience has simply shown that different individuals have not an equal power to cope with the parasites. ”

“ During this interval—the period of incubation—the body may organize a resistance sufficient to expel them.
We do not as yet thoroughly understand the forces which the human organism is able to array against these invading foes. Some of its methods of defence are, however, already intelligible to us, and we know enough, at all events, to give us an idea of the intensity of the conflict that is going on, and of the vigorous and powerful forces which the human organism is able to bring against its invading enemies. ”

“ There is in all animal organisms a certain innate power of resistance to germs of disease, and there is likewise in man a similar power of resistance to degeneracy.
The forces that operate to protect the individual operate also to shield the species by affording protection against evil inheritance. ”

“ All living beings eat one another or at any rate struggle against each other, plants as well as animals; and, apart from air and water, animals are almost entirely nourished by plants and other animals. It is obvious that in this perpetual struggle the less adapted and the less armed—and by arms we include the powers of reproduction, resistance to diseases and to cold, etc.—disappear, while the better adapted and the better armed persist. I confess I cannot understand the detractors of Darwin who are blind in face of these facts and hypnotized by certain conventional suggestions. ”

“ On contemplating its general circumstances, we perceive that any race of organisms is subject to two sets of conflicting influences. On the one hand by natural death, by enemies, by lack of food, by atmospheric changes, &c., it is constantly being destroyed. On the other hand, partly by the strength, swiftness and sagacity of its members, and partly by their fertility, it is constantly being maintained. These conflicting sets of influences may be conveniently generalized as—the forces destructive of race, and the forces preservative of race. ”

“ Finally, there comes a time when this resistance begins to fail, so that the earth, which never for a moment loses her grasp, commences and continues to prevail, and after a struggle, extended from twenty to thirty years, conquers, bringing the exhausted organism, which has daily approached nearer and nearer to her dead self, into her dead bosom. ”

“ But by virtue of this natural selection of our kind we have developed resisting power; to no germs do we succumb without a struggle, and to many—those that cause putrefaction in dead matter, for instance—our living frames are altogether immune. ”

“ The possession of such a power is moreover a distinction comparable with those which differentiate varieties and species. It is due to the development in the blood of specific substances which pervade the whole fluid. This development is exactly one of those "appropriate responses to [Pg 88] stimuli" which naturalists who incline to regard adaptation as a direct consequence of an environmental influence might most readily invoke as an illustration of their views. And yet all evidence is definitely unfavourable to the suggestion of an inheritance of the acquired power of resistance. ”

“ Every organism, from the commencement of its existence, struggles with a number of hostile influences: it struggles against animals which feed on it, and to which it is the natural food, against animals of prey and parasites; it struggles against inorganic influences of the most varied kinds, against temperature, weather, and other circumstances; but it also struggles (and this is much the most important!) , above all, against organisms most like and akin to itself. ”

“ He referred to experiments in which one-celled animals had during many generations acquired a special power of resistance against certain chemicals placed in their environment and had transmitted that resistance through many generationns after the chemicals had been withdrawn from the environment. ”

“ That the human organism, together with all its interdependent parts, organs and functions, is an inseparable whole—a Unit—subject absolutely to Natural Laws. As said St. Paul: "And whether one member suffer, all the members suffer with it." (Cor. 12-26.)
That disease, therefore, is likewise a unit with a diversity of manifestations which, like all conflicting elements, develop in the individual organism along the lines of least resistance, according to the weakness—hereditary or acquired—of the individual. This we term predisposition. ”

“ That is to say, the decreased multiplication of somatic cells in some cases, is not due to any exhaustion, but is caused by the rise of enemies or adverse conditions; as happens generally with introduced species of plants and animals which multiply at first enormously, and then, without any loss of reproductive power, begin to decrease under the antagonizing influences which grow up.↑ A Text Book of Human Physiology. ”

“ Deleterious Surroundings.—There can be little doubt that all unnatural and artificial modes of life tend to deterioration of the powers of resistance of the organism to disease. We see it exemplified in plant life in circumstances which are unnatural to the life of the plant, and the prevalence of certain constitutional tendencies among the inhabitants of crowded cities bears evidence to the same law.
Man, like other animals, was naturally intended to lead an outdoor life. ”

“ So that, on the whole, we may say that natural selection is ever waiting and watching for such combinations of germ-plasm as will give the resulting organisms the best possible chance in their struggle for existence; while, at the same time, it is remorselessly destroying all those combinations of germ-plasm which are handed over to the custody of organisms not so well fitted to their conditions of life. ”

“ The first was the great resisting power and vigor of the human organism, which we had gravely underestimated. The second, that power of adaptation to new circumstances, including even the attack of infectious diseases, which we call "survival of the fittest." The third, that great, sustaining, conservative power of nature—heredity. More cheering yet, these forces came, not merely fully armed, but bearing new weapons fitted for our hands. The vigor and unconquerable toughness of the human animal presented us with three glittering weapons, sunshine, food, and fresh air. ”

“ What, then, are those changes in the environment to which, by direct or indirect equilibration, the human organism has been adjusting itself, is adjusting itself now, and will continue to [526] adjust itself? And how do they necessitate a higher evolution of the organism?
Civilization, everywhere having for its antecedent the increase of population, and everywhere having for one of its consequences a decrease of certain race-destroying forces, has for a further consequence an increase of certain other race-destroying forces. ”

“ On this ground one must infer that, in accordance with the same law of natural selection, the bacteria of acute infections have met by natural selection each advance in the struggle of the host for immunity. Hence the fast and furious struggle between man and his microscopic enemies merely indicates to what extent natural selection has developed the ATTACK and the DEFENSE respectively. This struggle is analogous to the quick and decisive battles of the carnivora when fighting among themselves or when contending against their ancient enemies. ”

“ But when phylogenetically strange animals meet each other, they do not understand how to conduct a fight: natural selection has not had the opportunity of teaching them. The acute infections have the characteristics of being ancient enemies. ”

“ Such a part will often become inflamed, will often become subject to the action of bacteria which must have been in the body already, but which had been kept on the frontier by our powers of resistance. ”

“ I said, "with something alive floating in it."
"The foam, as you call it, bears a singular resemblance to the basic life principle, protoplasm, when seen under the microscope," replied the doctor.
"But those white things—" I began.
"The white things," he went on, "are the living remnants of a complex organism that has been destroyed. They are waging an unequal and hopeless battle against assimilation by the globules that surround them. These faithful guardians of the organism when alive still fight, and will continue to fight the enemy until, figuratively speaking, the last man falls." ”

“ Plainly, the body must have another set of resisting forces which is concerned in the final recovery. Although weakened by the poisoning and suffering from the disease, it does not yield the battle, but somewhat slowly organizes a new attack upon the invaders. ”

“ For what, expressed in mechanical terms, is the effect wrought on a species by some previously-unknown enemy, that kills such of its members as fail in defending themselves? The disappearance of those individuals which meet the destroying forces by the smallest preserving forces, is tantamount to the yielding of the species as a whole at the places where the resistances are the least. ”

“ Struggle for Life between, closely allied Animals and Plants often the most severe.
The struggle we have hitherto been considering has been mainly that between an animal or plant and its direct enemies, whether these enemies are other animals which devour it, or the forces of nature which destroy it. But there is another kind of struggle often going on at the same time between closely related species, which almost always terminates in the destruction of one of them. ”

“ But many of the means of animal defence are in themselves almost inscrutable; we see the weapon used, but cannot account for its present existence. Natural selection may explain the improvement and survival of such useful organs, but their origin is still obscure. ”

“ It is plain, then, that the human body is not helpless in the presence of the bacteria of disease, but that it is supplied with powerful resistant forces. It must not be supposed, however, that the outline of the action of these forces just given is anything like a complete account of the matter ”

“ Hence, in parasites and some forms of life which live under simple conditions, we have the phenomena of degeneration, or a passage from a more complex to a more simple condition.
Revolution in organic life is the destruction of one organism or group of organisms, and the replacement in its stead of a wholly different organism or group of organisms. During hard times there may be much revolution, or replacement of one set of organic forms by another set of organic forms. ”

“ That biology has been forced, through its own advances, to recognize the struggle-survival doctrine, upon which she earlier staked so much as the cause of evolution, is really of very subordinate importance in this way, needs to be set forth to the general public far more emphatically and convincingly than it has been. ”

“ This struggle falls, moreover, at a time of year when food is generally abundant, and perhaps the effect chiefly produced would be the alteration of sexual characters, and the selection of individual forms, no way related to their power of obtaining food, or of defending themselves from their natural enemies, but of fighting one with another. ”

“ In the progress of medical science man may be wholly relieved from the worst and most [Pg 154] obscure parasites that have ever infested him, without waiting for their evolution into some other type of animal that does not desire or need to prey upon the human system, or without waiting to have the human organism developed into one that will not be exposed to such causes of suffering or death. We know already that very simple precautions will ward off from man some of the most subtle of these enemies ”

“ Here we have the example of another phenomenon which seems to contradict certain hypotheses of Spencer and Darwin. If it is true that, in the struggle for existence, animals have always perfected those capabilities which are most useful to them in defending themselves, and have gradually left behind, with the generations that have succumbed, all dispositions of the organism which were pernicious to the preservation of the species, why have they not succeeded in freeing themselves from trembling? ”

“ But how can this oversight on the part of an enemy so affect the bodies and through them the germ-cells of such individuals as to develop so high a degree of protective coloration? Or how, indeed, could any of numerous adaptive structures which one can think of, such as the color or scent of flowers to lure insects for cross-pollenation, the various grappling devices on many seeds to secure wide distribution by animals, or the like, have been directly produced by use or disuse or by any variation produced in them by the agents to which they are adapted? ”

“ Disuse, aided sometimes by natural selection, will often have reduced organs when rendered useless under changed habits or conditions of life; and we can understand on this view the meaning of rudimentary organs. But disuse and selection will generally act on each creature, when it has come to maturity and has to play its full part in the struggle for existence, and will thus have little power on an organ during early life ”

“ That a new external action may be met by a new internal action, it is needful that it shall either continuously or frequently be borne by the individuals of the species, without killing or seriously injuring them; and shall act in such way as to affect their functions. And we find that many of the environing agencies—evil or good—to which organisms have to be adjusted, are not of these kinds: being agencies which either do not immediately affect the functions at all, or else affect them in ways that prove fatal. ”