Part 7 (2/2)
A second difficulty is in getting the drug to produce its effect at the right point. A few diseases, as we have noticed, are produced by bacteria which distribute themselves almost indiscriminately over the body; but the majority are somewhat definitely localized in special points. Tuberculosis may attack a single gland or a single lobe of the lung. Typhoid germ is localized in the intestines, liver, spleen, etc. Even if it were possible to find some drug which would have a very specific effect upon the tuberculosis bacillus, it is plain that it would be a very questionable method of procedure to introduce this into the whole system simply that it might have an effect upon a very small isolated gland. Sometimes such a bacterial affection may be localized in places where it can be specially treated, as in the case of an attack on a dermal gland, and in these cases some of the germicides have proved to be of much value. Indeed, the use of various disinfectants connected with abscesses and superficial infections has proved of much value. To this extent, in disinfecting wounds and as a local application, the development of our knowledge of disinfectants has given no little aid to curative medicine.
Very little success, however, has resulted in the attempt to find specific drugs for specific diseases, and it is at least doubtful whether many such will ever be found. The nearest approach to it is quinine as a specific poison for malarial troubles. Malarious diseases are not, however, produced by bacteria but by a microscopic organism of a very different nature, thought to be an animal rather than a plant. Besides this there has been little or no success in discovering specifics in the form of drugs which can be given as medicines or inoculated with the hope of destroying special kinds of pathogenic bacteria without injury to the body.
While it is unwise to make predictions as to future discoveries, there seems at present little hope for a development of curative medicine along these lines.
VIS MEDICATRIX NATURAE.
The study of bacterial diseases as they progress in the body has emphasized above all things the fact that diseases are eventually cured by a natural rather than by an artificial process. If a pathogenic bacterium succeeds in pa.s.sing the outer safeguards and entering the body, and if it then succeeds in overcoming the forces of resistance which we have already noticed, it will begin to multiply and produce mischief. This multiplication now goes on for a time unchecked, and there is little reason to expect that we can ever do much toward checking it by means of drugs. But after a little, conditions arise which are hostile to the further growth of the parasite. These hostile conditions are produced perhaps in part by the secretions from the bacteria, for bacteria are unable to flourish in a medium containing much of their own secretions.
The secretions which they produce are poisons to them as well as to the individual in which they grow, and after these have become quite abundant the further growth of the bacterium is checked and finally stopped. Partly, also, must we conclude that these hostile conditions are produced by active vital powers in the body of the individual attacked. The individual, as we have seen, in some cases develops a quant.i.ty of some substance which neutralizes the bacterial poisons and thus prevents their having their maximum effect. Thus relieved from the direct effects of the poisons, the resisting powers are recuperated and once more begin to produce a direct destruction of the bacteria. Possibly the bacteria, being now weakened by the presence of their own products of growth, more readily yield to the resisting forces of the cell life of the body. Possibly the resisting forces are decidedly increased by the reactive effect of the bacteria and their poisons. But, at all events, in cases where recovery from parasitic diseases occurs, the revived powers of resistance finally overcome the bacteria, destroy them or drive them off, and the body recovers.
All this is, of course, a natural process. The recovery from a disease produced by the invasion of parasitic bacteria depends upon whether the body can resist the bacterial poisons long enough for the recuperation of its resisting powers. If these poisons are very violent and produced rapidly, death will probably occur before the resisting powers are strong enough to drive off the bacteria. In the case of some diseases the poisons are so violent that this practically always occurs, recovery being very exceptional. The poison produced by the teta.n.u.s bacillus is of this nature, and recovery from lockjaw is of the rarest occurrence. But in many other diseases the body is able to withstand the poison, and later to recover its resisting powers sufficiently to drive off the invaders. In all cases, however, the process is a natural one and dependent upon the vital activity of the body. It is based at the foundation, doubtless, upon the powers of the body cells, either the phagocytes or other active cells. The body has, in short, its own forces for repelling invasions, and upon these forces must we depend for the power to produce recovery.
It is evident that all these facts give us very little encouragement that we shall ever be able to cure diseases directly by means of drugs to destroy bacteria, but, on the contrary, that we must ever depend upon the resisting powers of the body. They teach us, moreover, along what line we must look for the future development of curative medicine. It is evident that scientific medicine must turn its attention toward the strengthening and stimulating of the resisting and curative forces of the body. It must be the physician's aim to enable the body to resist the poisons as well as possible and to stimulate it to re-enforce its resistant forces. Drugs have a place in medicine, of course, but this place is chiefly to stimulate the body to react against its invading hosts. They are, as a rule, not specific against definite diseases. We can not hope for much in the way of discovering special medicines adapted to special diseases. We must simply look upon them as means which the physician has in hand for stimulating the natural forces of the body, and these may doubtless vary with different individual natures. Recognising this, we can see also the logic of the small dose as compared to the large dose. A small dose of a drug may serve as a stimulant for the lagging forces, while a larger dose would directly repress them or produce injurious secondary effects. As soon as we recognise that the aim of medicine is not to destroy the disease but rather to stimulate the resisting forces of the body, the whole logic of therapeutics a.s.sumes a new aspect.
Physicians have understood this, and, especially in recent years, have guided their practice by it. If a moderate dose of quinine will check malaria in a few days, it does not follow that twice the dose will do it in half the time or with twice the certainty.
The larger doses of the past, intended to drive out the disease, have been everywhere replaced by smaller doses designed to stimulate the lagging body powers. The modern physician makes no attempt to cure typhoid fever, having long since learned his inability to do this, at least if the fever once gets a foothold; but he turns his attention to every conceivable means of increasing the body's strength to resist the typhoid poison, confident that if he can thus enable the patient to resist the poisoning effects of the typhotoxine his patient will in the end react against the disease and drive off the invading bacteria. The physician's duty is to watch and guard, but he must depend upon the vital powers of his patient to carry on alone the actual battle with the bacterial invaders.
ANt.i.tOXINES.
In very recent times, however, our bacteriologists have been pointing out to the world certain entirely new means of a.s.sisting the body to fight its battles with bacterial diseases. As already noticed, one of the primal forces in the recovery, from some diseases, at least, is the development in the body of a substance which acts as an antidote to the bacterial poison. So long as this ant.i.toxine is not present the poisons produced by the disease will have their full effect to weaken the body and prevent the revival of its resisting powers to drive off the bacteria. Plainly, if it is possible to obtain this ant.i.toxine in quant.i.ty and then inoculate it into the body when the toxic poisons are present, we have a means for decidedly a.s.sisting the body in its efforts to drive off the parasites. Such an antidote to the bacterial poison would not, indeed, produce a cure, but it would perhaps have the effect of annulling the action of the poisons, and would thus give the body a much greater chance to master the bacteria. It is upon this principle that is based the use of ant.i.toxines in diphtheria and teta.n.u.s
It will be clear that to obtain the ant.i.toxine we must depend upon some natural method for its production. We do not know enough of the chemical nature of the ant.i.toxines to manufacture them artificially. Of course we can not deny the possibility of their artificial production, and certain very recent experiments indicate that perhaps they may be made by the agency of electricity. At present, however, we must use natural methods, and the one commonly adopted is simple. Some animal is selected whose blood is harmless to man and that is subject to the disease to be treated. For diphtheria a horse is chosen. This animal is inoculated with small quant.i.ties of the diphtheria poison without the diphtheria bacillus. This poison is easily obtained by causing the diphtheria bacillus to grow in common media in the laboratory for a while, and the toxines develop in quant.i.ty; then, by proper filtration, the bacteria themselves can be removed, leaving a pure solution of the toxic poison. Small quant.i.ties of this poison are inoculated into the horse at successive intervals. The effect on the horse is the same as if the animal had the disease. Its cells react and produce a considerable quant.i.ty of the ant.i.toxine which remains in solution in the blood of the animal. This is not theory, but demonstrated fact. The blood of a horse so treated is found to have the effect of neutralizing the diphtheria poison, although the blood of the horse before such treatment has no such effect. Thus there is developed in the horse's blood a quant.i.ty of the ant.i.toxine, and now it may be used by physicians where needed.
If some of this horse's blood, properly treated, be inoculated into the body of a person who is suffering from diphtheria, its effect, provided the theory of ant.i.toxines is true, will be to counteract in part, at least, the poisons which are being produced in the patient by the diphtheria bacillus. This does not cure the disease nor in itself drive off the bacilli, but it does protect the body from the poisons to such an extent as to enable it more readily to a.s.sert its own resisting powers.
This method of using ant.i.toxines as a help in curing disease is very recent, and we can not even guess what may come of it. It has apparently been successfully applied in diphtheria. It has also been used in teta.n.u.s with slight success. The same principle has been used in obtaining an antidote for the poison of snake bites, since it has appeared that in this kind of poisoning the body will develop an antidote to the poison if it gets a chance. Horses have been treated in the same way as with the diphtheria poison, and in the same way they develop a substance which neutralizes the snake poison. Other diseases are being studied to-day with the hope of similar results. How much further the principle will go we can not say, nor can we be very confident that the same principle will apply very widely. The parasitic diseases are so different in nature that we can hardly expect that a method which is satisfactory in meeting one of the diseases will be very likely to be adapted to another. Vaccination has proved of value in smallpox, but is not of use in other human diseases. Inoculation with weakened germs has proved of value in anthrax and fowl cholera, but will not apply to all diseases. Each of these parasites must be fought by special methods, and we must not expect that a method that is of value in one case must necessarily be of use elsewhere. Above all, we must remember that the ant.i.toxines do not cure in themselves; they only guard the body from the weakening effects of the poisons until it can cure itself, and, unless the body has resisting powers, the ant.i.toxine will fail to produce the desired results.
One further point in the action of the ant.i.toxines must be noticed. As we have seen, a recovery from an attack of most germ diseases renders the individual for a time immune against a second attack. This applies less, however, to a recovery after the artificial inoculation with ant.i.toxine than when the individual recovers without such aid. If the individual recovers quite independently of the artificial ant.i.toxine, he does so in part because he has developed the ant.i.toxines for counteracting the poison by his own powers. His cellular activities have, in other words, been for a moment at least turned in the direction of production of ant.i.toxines. It is to be expected, therefore, that after the recovery they will still have this power, and so long as they possess it the individual will have protection from a second attack. When, however, the recovery results from the artificial inoculation of ant.i.toxine the body cells have not actively produced ant.i.toxine. The neutralization of the poisons has been a pa.s.sive one, and after recovery the body cells are no more engaged in producing ant.i.toxine than before. The ant.i.toxine which was inoculated is soon eliminated by secretion, and the body is left with practically the same liability to attack as before. Its immunity is decidedly fleeting, since it was dependent not upon any activity on the part of the body, but upon an artificial inoculation of a material which is rapidly eliminated by secretion.
CONCLUSION.
It is hoped that the outline which has been given of the bacterial life of Nature may serve to give some adequate idea of these organisms and correct the erroneous impressions in regard to them which are widely prevalent. It will be seen that, as our friends, bacteria play a vastly more important part in Nature than they do as our enemies. These plants are minute and extraordinarily simple, but, nevertheless, there exists a large number of different species. The number of described forms already runs far into the hundreds, and we do not yet appear to be approaching the end of them. They are everywhere in Nature, and their numbers are vast beyond conception. Their powers of multiplication are inconceivable, and their ability to produce profound chemical changes is therefore unlimited. This vast host of living beings thus const.i.tutes a force or series of forces of tremendous significance. Most of the vast mult.i.tude we must regard as our friends. Upon them the farmer is dependent for the fertility of his soil and the possibility of continued life in his crops. Upon them the dairyman is dependent for his flavours. Upon them important fermentative industries are dependent, and their universal powers come into action upon a commercial scale in many a place where we have little thought of them in past years. We must look upon them as agents ever at work, by means of which the surface of Nature is enabled to remain fresh and green. Their power is fundamental, and their activities are necessary for the continuance of life. A small number of the vast host, a score or two of species, unfortunately for us, find their most favourable living place in the human body, and thus become human parasites.
By their growth they develop poisons and produce disease. This small cla.s.s of parasites are then decidedly our enemies. But, taken all together, we must regard the bacteria as friends and allies. Without them we should not have our epidemics, but without them we should not exist. Without them it might be that some individuals would live a little longer, if indeed we could live at all. It is true that bacteria, by producing disease, once in a while cause the premature death of an individual; once in a while, indeed, they may sweep off a hundred or a thousand individuals; but it is equally true that without them plant and animal life would be impossible on the face of the earth.
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