# Popular Science Monthly/Volume 61/May 1902/Infectious Diseases

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* INFECTIOUS DISEASES.
By ALFRED SPRINGER, PH.D.,
CINCINNATI, OHIO.
INFECTIOUS diseases have devastated more homes than all wars combined, and a check to their ravages would be the greatest boon suffering mankind can hope to achieve.
These diseases are supposed to owe their origin to the activity of ferments, enzymes, sporozoa or other ultra-microscopical organisms, consequently they must have some reactions in common with other phenomena depending upon the same agencies.
If true scientific reasoning is based upon inductive methods, namely, 'the endeavor from the much which is observable to arrive at a little which may be verified and is indubitable' then truly our knowledge of ferments is very meager—in fact practically everything we know is deduced from observing the alcoholic yeast ferments, and this for the following reasons: First, they have been employed for many ages. Second, they are larger than the other ferments. Third, they can be studied without jeopardizing fellowmen. Fourth, their chemical effects can be traced in the laboratory, qualitatively and quantitatively, an I last, but not least, their study is not beset with those difficulties which immediately present themselves when effects are produced upon higher differentiated types such as man.
I shall only call attention to such properties which undoubtedly many pathogenic bacteria hold in common with them, namely, we know that these ferments multiply with exceeding rapidity—that they can withstand great ranges of temperature and many chemicals poisonous to man—that they can accommodate themselves to abnormal conditions and remain dormant until suitable conditions again arise and that by their immense numbers much organic material is destroyed. We know, on the other hand, that these ferments have their enemies which can either suppress them entirely or to such an extent as to make them harmless. We know that the introduction of other ferments in the same medium, making use of one of their essential nutrients, may cause a total cessation of their activity—we know that their own excreta or similar products act as poisons upon them. We also know that ferments and enzymes are selective in their foods, probably not from volition, but for reasons of food assimilation.
It is a well-known fact that but an imponderable quantity of a specific ferment is required to start fermentation and this, owing to ​reproduction, increases in a geometrical proportion, so that in a comparatively short time the whole mass is attacked. Thus a small amount of yeast will start the dissociation of thousands of gallons of a mash—the bacteria, in a septic tank, derived from the human digestive tracts, liquefy in twelve hours all the sewage of a household, including the paper and other cellulose matter. Pathogenic germs, in media such as nutrient gelatine, agar-agar, blood serum, etc., also develop quite rapidly; nevertheless the progress of infectious diseases is comparatively slow and frequently localized.
Since many pathogenic germs are present in the air we breathe, in the water we drink, and in the soil we come in contact with, infectious diseases seemingly ought constantly prevail; this not being the case, it has been assumed that the system itself under normal conditions can withstand their attack. Predisposition, on the other hand, betokens a weakened system, i.e., decreased vitality, or one in which the way for the entrance of the germs has been paved. From this it may be concluded that the so-called specific disease germs generally present are no more dangerous than the predisposing media. Immunity can be obtained either by avoiding the pathogenic germs or the predisposing cause. At present means are suggested to isolate the consumptive and destroy the intermediate-bearing host, both in malaria and yellow fever. It is not even known whether other carriers equally dangerous exist.
The destruction of the predisposing cause certainly is more humane, and the one to be sought for. Unfortunately success has been limited to but few of the many diseases known to be of an infectious nature. Probably failure is largely due to ignorance of causes producing immunity, and in fact every theory so far advanced has been badly battered by numerous failures of substantiation.
Recent experiments indicate that specific ferments can only dissociate specific foods, i.e., the assimilable ones for any one class of ferments do not constitute a wide range. Furthermore, it has been proved that micro-organisms can either be antagonistic to each other, i.e., one can change some nutrient essential to the other's existence, or synergetic, where one is dependent upon the other for its food—and, in some cases, they may be indifferent where the food of the one is not that of the other.
Synergetic action plainly shows how limited is the dissociating power of micro-organisms. Thus an albuminoid is first converted into an ammonia compound by one class of ferments, a second class produces nitrites and a third nitrates. In the absence of the first, neither nitrites nor nitrates can be formed, and in the absence of the second no nitrate will appear. Still more striking—most exact experiments have shown that both ferments and enzymes cannot assimilate food ​chemically and physically the same as some of their best nutrients—save in having opposite powers of rotation.
Taking into consideration that micro-organisms can withstand temperatures and chemicals fatal to man, the slow development of infectious diseases is most probably intimately connected with an insufficiency of assimilable food. This food it may be assumed can only be obtained by symbiosis either with other micro-organisms or products of cell activity in the system itself.
It is claimed that the Anopheles mosquito is the intermediate host of the human malaria and the Culex that of the bird, but not vice versa. These mosquitoes undoubtedly do not select the spores of their respective parasites and avoid the others, but there must exist conditions in the system of the respective mosquito which allow of the propagation of one kind and not the other—and these conditions, I take it, are food assimilable ones.
White mice are immune to splenic fever, other mice very susceptible. Since the blood of white mice is more alkaline than that of the others—and such blood when made less alkaline becomes a good medium for the cultivation of the anthrax bacillus—it has been claimed that the alkalinity produces the immunity. On the other hand it has been found that alkalies are not particularly harmful to the anthrax bacillus—therefore, it seems to me, that alkalinity, as such, is less of a factor than its consequent effects upon the nutrients of the bacillus.
Pasteur demonstrated that micro-organisms select one of two optical isomers, and Fischer proved that it is not only a question of optical antipodes in different sugars, but amongst a great number of geometrical forms few fulfil the requirements of the cells—furthermore he is of the opinion that many chemical processes in the system are affected by molecular geometry.
The albuminoids are the most important constituents of the living cells and since they are synthetically formed from the carbohydrates of the plants, Fischer believes that the geometrical structures of their molecules, as far as asymmetry is concerned, are essentially like those of the natural hexoses. Thus it seems that configuration plays a most important role in making food assimilable—be it in converting inactive into active modifications or vice versa or the production of one optical isomer instead of the other, or some other change of configuration, the consequence would be a different behavior toward the ferments, enzymes and sporozoa.
We now come to another feature which also may be of physiological interest, namely: the fact that the alkaloids largely used for therapeutical purposes, such as quinine, cinchonine, quinicine, conchinine, strychnine, brucine and morphia can, like micro-organisms, bi-part racemic forms. Thus cinchonine separates as salt from the inactive ​modification insoluble: l-Tartaric acid; d-Methoxylsuccinic acid; d-Mandelic acid. Penicillium glaucum destroys: d-Tartaric acid; l-Æthoxysuccinic acid; l-Mandelic acid. Lewkowitch's schizomycetes destroy: l-Tartaric acid; d-Mandelic acid. Strychnine separates: l-Lactic acid; l-Æthoxysuccinic acid. Many other examples can be cited, the principal difference being that the alkaloids separate the insoluble optical isomer and the micro-organisms make use of one of the optical isomers to build up their own structure.
The bi-partic powers of the alkaloids are as limited as those of the micro-organisms; thus strychnine can bi-part lactic acid, cinchonine malic but not lactic acid, etc., and most likely two acids bi-parted by the same base have analogous configuration.
From these arguments, I take it that predisposition and immunity are intimately connected with stereo-chemical changes, i.e., where the configuration, according to Fischer, of the nutrient, on the one hand, and the ferments, enzymes, sporozoa, etc., on the other, must be to each other as lock and key. Moreover, I believe that infectious diseases are not caused by any one class of ferments, but by many acting synergetically. In line with these results it strikes me that predisposition is a condition well suited to act synergetically when the missing ferment presents itself. Immunity, on the other hand, betokens the absence of a number of active synergetic ferments, owing to lack of requisite configurations.
While this suggestion may seem to offer one hazy hypothesis for another equally hazy, it opens a broader field for investigation, it admits of better explanations of observed results, and it agrees with our ideas that the demolition of complex organic materials, such as blood and the tissues, takes place step-like and not abruptly.
Surely some day physiological chemistry will be sufficiently powerful to shed its light through the mist now surrounding the so-called vital processes—clearly define the differences between the healthy and the disease-disturbed systems—teach us how to preserve the former and counteract the latter, by other than merely empirical methods.
When that day comes, infectious diseases like tuberculosis will no longer rob the stricken patient of all hope and cause him to be a constant menace, dreaded even by those who love him most dearly. When that day comes, parents no longer need be haunted by the fear that predisposition be transmitted to their children born and unborn.