If we grant to Metchnikoff the truth of his premise, that extinct species have been killed off by parasites, we are faced with the need to determine why some species succumb to the attacks of parasites while others proved highly resistant to them. Few animals are free of parasites; yet, in some instances they are relatively harmless. We suggest that the real cause of the disappearance of species is the cause that renders them susceptible to parasitic attack, or in other words, the cause that reduces their fitness to live. Fat organisms, giant organisms, acromegalic forms, parasitic organisms, predatory organisms, beasts of prey--insectivores, carnivores, cannibals, etc., etc.,--plant assassins and the like have passed from the scene in great numbers, while normally constituted organisms and those that continue to live non-predaciously have survived. Even many predacious animals have retained a great measure of their original ability to protect themselves.
In thinking of the survival for great stretches of time of great numbers of species of plants and animals, let us not overlook the survival, through vast periods, of the human species. Compared to the great length of time that man has been on the earth, the "medical art" is but a fledgling. Man, like the animals, survived for a long period of time when there was no "medical art," by reason of the fact that he is also possessed of great powers of resistance and self-repair.
It is assumed by the medical profession that in epidemics the so-called epidemic disease spreads by infection or contagion. By one means or another the disease is transmitted from patient to patient. This assumption, while apparently borne out by experience, fails to account for the origin of the disease. How does the disease spread from patient to patient until it has come into existence? This question may seem like the old one of which came first--the hen or the egg; but it is a question the correct answer to which would be of great practical importance.
For the sake of having somebody to begin with, let us start with the Biblical Adam and Eve and work down from there. Did the first man have smallpox; did he have bubonic plague; did he have cholera; did he have gonorrhea; did he have syphilis; did he have measles or chicken pox? If not, how many generations of men lived and died before the birth of the first individual who developed one of these supposed infectious or contagious diseases? Where did he "catch it?" With what prior case did he come in contact? Where did the first man to have smallpox come in contact with the disease, that he acquired the infection? With what first case of yellow fever did the mosquito come in contact, that he could convey the disease to another man? How did the first case of gonorrhea develop?
When we ask these questions, it becomes self-evident that the first case of every so-called infectious or contagious disease had to arise without contact with a prior case. If we think on this fact a little, it becomes equally evident that if one case can so arise, millions of cases can arise in the same manner in which the first case arose. Then we are faced with the question: in every epidemic, how many cases arise as did the first case and how many cases arise from contact with another case?
Discussing poliomyelitis, Cecil's Textbook of Medicine, fifth edition, p. 77, says: "The paradox of the isolated case remote from civilization, on the one hand, and on the other the epidemic force which offers a picture of mass group infection is well known but unexplained." Isolated cases of all so-called infectious diseases are well known; the phenomenon is not confined to poliomyelitis. If we but stop and think a minute, we will understand that the first case of every so-called epidemic disease that ever developed was, even though the patient was among friends, an isolated case. It could not, in the very nature of things, have been the result of "infection" by a prior case. Is it not possible that every case of every so-called infectious or contagious disease develops in precisely the same way that the first case develops?
If we have cases that develop de novo and cases which arise from transmission, how do we differentiate between these two classes of disease? If it can be shown that one case developed after contact with another case, is this enough to demonstrate that the second case arose out of the contact and did not arise de novo? If disease can arise in both ways, it is quite evident that to avoid epidemics we must avoid the de novo evolution of the first case and it is precisely here that Hygiene is of greatest value.
What is the reason, if contact with a case of infectious or contagious disease accounts for its spread, that all who contact the case or cases do not develop the disease. It is not enough to reply that these fortunate individuals are immune unless it can be explained what is meant by immunity and the reasons for the immunity are given. Immunity is a mere word and as it is at present used, covers a world of ignorance. We want a rational explanation. If germs are ubiquitous and are capable of infecting man, why are not all infected? Why is contact with a case of disease ever essential to infection? If the germs are everywhere, why can they not produce infection without the intermediary of a prior case? If the prior case is essential, how did the first case arise?
What is the essential difference between what is called immunity and health. Does immunity rest upon the same factors of existence that health rests upon? If we build and maintain a high state of health, are we immune? Or is immunity a pathological state, arising out of infection, as is now the general view of the medical profession and its rulers in the bacteriological field. Do we become immune by first becoming sick? Is sickness the route to immunity?
It is the condition of the individual and not the so-called contagion that determines the character of a disease. If the contagion determines the character of the disease, each person in the community, certainly each one in a family, would have it with equal certainty. As a matter of fact, the same disease may be malignant in one case and benignant in another, the difference being determined, not by the contagion, but by the patient's vital states. In the same family the so-called contagious disease may differ in the different individuals, whether the disease is smallpox, diptheria, scarlatina or measles.
The following classifications of some of the more common so-called contagious or infectious diseases have been made by medical classifiers.
Small Pox: discrete, confluent, or malignant