The principles of Continuity and Unity, which underlie all of modern science and which permeate all of its literature, have never found an acceptance in the field of medicine, and particularly in the field of pathology, its causation and development. By this principle of the Uniformity of Nature is understood the principle that there are no breaks in the operations of natural laws and processes; that the sequence of events in Nature are stable and regular, one development growing out of the preceding and giving rise to the succeeding one. Hygienists have, from the beginning, recognized the operation of this principle in pathological development--they have perceived more or less clearly the unity and continuity of the pathological process. Dr. Jennings especially emphasized this principle.

Though Graham had some conception of the evolution of pathology, he seems not to have stressed the principle sufficiently nor to have developed his ideas extensively. It is interesting to note that in his work on cholera (1833) he briefly traced the evolution of pathology thus: "reductions of vital power" (enervation), a "general withering" of all the organs, enfeeblement of "each particular function," lowered resistance, and "chronic disease, corresponding in character with the peculiarities of circumstances, of causes, and of individual idiosyncracies, or predispositions, have been, generally by slow, and imperceptible degrees, developed in the human system."

Jennings was the first to lay stress on the principle of evolution in pathology. Following him, Page and Rabagliati each attached considerable importance to this principle. Tilden has emphasized this principle more than any other man and has developed it more extensively than all of the others combined. The present writer has stressed the evolution of pathology for years and feels that he has extended our understanding of it.

Pathology is a department of general biology. It is almost as old as life and it should be recognized that human maladies constitute but a narrow fringe along the borders of the great sea of pathology seen in the plant and animal world. The common man can, if he will try, understand the seamy side of biology as well as any other phase of it; if he can divest himself of his tlieologico-medical coating of fallacies and farces.

Pathology deals with the changes which the organism undergoes as a result of the action of pathogenic influences. It is the regressive metamorphosis of the tissues of the body; the breaking down and deterioration of the living organism. Pathology is the consequence of the combined "action" of all the impairing influences to which the organism is subjected. Cause is multiple, not single.

There are two kinds of processes in the living body which are called disease. First, there is a progressive deterioration or degeneration of the body which begins in early life, sometimes in embryonic life, or even in the germ cell, and which culminates in death, and which every one thinks of as normal and natural. Second, there are the many forms of acute and chronic defensive reactions of the body, which are designed to save life, restore health, and prevent the deterioration and which every one regards as abnormal, evil and destructive. We witness a race between two great tendencies-- the one progressive and advancing, the other retrogressive and degenerating.

Healing processes and physiological actions, with which the body resists the causes of the impairment, and the efforts to repair the damages done, are not properly termed pathology. The cause of this is "life"--the causes of pathology are anti-vital, abnormal. Vital or physiological actions are orthopathic, always. There is a fundamental difference between physiology and pathology, between life and death.

By the continuity of pathology I mean that related sequence of progressive effects which binds all the "local" pathological units together, both in time and place, so that the innumerable "diseases" are not single independent "diseases," but integral parts of the whole process. Pathology is of a very complicated nature which grows, in a process of evolution, from the simplest conditions to more and more complicated combinations.

Evolution, like many terms loosely employed by science, has no definite meaning. It is derived from the latin, evolvo, meaning to roll out, to unfold, to open. Pathological evolution is the mode of educing the extension and completion of the process of degeneration and may be fairly applied to the aggregate of so-called "diseases," always presupposing that the reverse metamorphosis, which it represents, cannot take place without the continual activity of causation. By the evolution of pathology we mean the continuous series of stages or steps by which the first faint beginnings of "disease" develop, due to the persistence of their causes, into formidable and advanced pathological conditions. It is a slow, gradual, insidious process, which, due to the present manner of regarding "disease," is unrecognized. Its terminal manifestations, it is true, are recognized and are called degenerative diseases of later life; but these are called this only because it usually requires a life time, thanks to the stubborn and never-ceasing resistance of the body, for the degeneration to become great enough to be recognized as such, and because we have not learned to see that the process of degeneration has gone on for years before it finally culminated in these conditions.

At a necropsy, the chest of a young man who had died of tuberculosis of the lungs was opened revealing an ugly abscess of one of the lobes of the lungs. "There," said one of the physicians present, "I don't want to look any further for the cause of death." But he was looking at the end, not at the beginning of the young man's trouble. How come the abscess there? How come the liver diseased? How and why do congestions, inflammations, etc., develop? Such conditions as were revealed in opening this young man's chest do not come into existence full-blown, any more than trees or flowers do.

"Diseases" never come butt-end first and Jennings truly said: "The ground is first broken at the surface, and there is a regular gradation from the summit level of physical soundness to the stagnant fenny regions of disorder. It takes a great while and an amazing amount of opposing, noxious influences to reduce a healthy vigorous system to a diseased state, according to the common acceptation of that term".--Philosophy of Human Life, p. 199.

Medical men usually begin at the finish to diagnose a "disease." After the patient is dead, they hold a post-mortem and their findings are handed out as a diagnosis. They find a cancer, a fibroid tumor, an abscess and these are given as the cause of death. But these things are effects. They are the results of causes that are not discoverable at the necropsy, causes that have ceased. They see the finished product, not its initial beginnings and, hence, are not able to learn anything that is of value in preventing such developments.