According to medical science, pathology is the science of disease--that branch of medical science which treats of the modifications of function and structure of organs caused by disease. Disease defined is: inharmonious action of one or more of the various organs, owing to functional or structural change.

There is special pathology, which means analyzing disease. This is divided into internal or medical, and external or surgical, pathology. Then there is comparative pathology, which considers a study of diseases in man, animals, and vegetables; experimental pathology, and general pathology.

General pathology defines terms and fixes meanings; determines the laws of morbid phenomena, determines causes, defines symptoms, names diseases.

Pathology is a description of the body, and the organs which compose it, when they are laboring under the effects of abnormal, unusual, and perverting influences.

Physiology is the study of the body and its organs in that state known as health, and under influences that give health and strength.

Pathology, then, is that state of the body known as bad health, while physiology is that state of the body known as good health.

Disease is inharmony, and health is harmony. Both are different states of one and the same thing.

When we study pathology in connection with the influences that produce it, we learn in time to recognize real cause in its effect.

To study effectually the phenomenon pathology--disease--we must combine with it physiology--health--and etiology--cause.

To study pathology--to note change in function and structure--without a correct understanding of the cause of the change, leads nowhere. To study physiology-to study the secretions and excretions from men en masse, like a composite picture--will show an average--show about what an average individual should secrete and excrete under a given environment and a measured dietary. This is good as far as it goes, but no approximation can do more than give general knowledge of physiology and pathology. This generalization will give a like knowledge of dietetics, hygiene, and all branches of medical science.

Morbific effects will be found following certain morbific causes; but on closer investigation it will be found that there are exceptions to every cause--that there is no cause that always produces the same effect; hence pathology, physiology, their causes and effects, must be studied, not only in a general way, but in a special way, and the reason for exceptions must be as thoroughly understood as the rules.

Health and disease are related in that they are two phases of one state, and neither can be known without contrasting it with the other.

Living organisms are unstable. Their state must vary with the changes that take place in the environing influences.

The phenomena recognized as different acts of life are not dependent on some mysterious force outside of the body--some vital energy animating the body--but are simply actions and reactions produced by external agents.

For example, when external variations are slight, adjustments are readily made in those of a full measure of health, but not so readily adjusted in those with resistance broken down. Where the temperature falls forty to sixty degrees in a day or night, the most robust will suffer more or less from the adjustment, and the delicate may be killed.

Pathology given exclusive attention is a fruitless study. Health in all its phases must be studied, and cause and effect must be found in everything that affects the body.

The general study of pathology today too frequently starts with an established state of the blood or the organs of the body. The primary causes are ignored or not thought of. For example: Typhoid fever is thought of as cause, which leaves, when over, modifications which persist; being too slight to be recognized, they nevertheless continue their evolution. Ten to fifteen years later a heart, lung, liver, or kidney disease develops, which is ascribed to the changes wrought by the initial fever. A correct way to view these phenomena is to recognize the typhoid as an accidental but possible link in a morbific chain started in perverted nutrition, back perhaps in childhood, or back farther in a nutritional diathesis, that makes the development of a morbid chain of perverted nutrition, with possible links of typhoid, pneumonia, catarrhal inflammations, et al.