The Interdependence of Diseases. - Narrow Specialities and Broad Departments in the Practice of Medicine. - Normal Diet. - Errors in Diet. - The Diet of Disease. - Food, Heat, and Motion. - Getting Fat and Getting Thin. - Alcohol, its Proper Place in Diet. - Regimen, the Regulation of Habits. - House-Drainage. - Importance of Sleep. - Proper Hours for Meals. - Disinfection. - Pseudo-Medical Dogmas, Allopathy, Hydropathy, Homoeopathy, Kinesipathy. - Rational Medicine.

In the practice of Rational Medicine, there are many subjects upon which the wise Physician is always glad to find that his patient has some knowledge as well as himself. Among these I know of none more important than the Interdependence of Diseases and the Principles of Diet and Regimen.

There are few medical questions which so test the depth and extent of a doctor's acquirements as the interdependence of diseases - by which I mean, the way in which one disease leads to another, substitutes another, aggravates, or relieves another; the way in which disease appearing at one part of the body depends upon the derangement of another part, perhaps distantly separated; the way in which disease of one kind in an ancestor, leads to disease of several different kinds in the descendants; the way in which one general morbid cause may produce different effects upon different persons, according to the conditions of health in which they happen to be at the time; and numberless other similar phenomena.

These are matters of the highest importance in the right management and treatment of disease; yet they are so little understood, that the pains taken by a conscientious doctor in their investigation are not appreciated by the majority of persons. Thus it is that patients so often fail to discriminate between the wisdom of the man who will not prescribe for a part of the body until he has learnt the condition of the whole, and the ad captandum ignorance of another man who will prescribe unhesitatingly for a disorder of the whole body without previously ascertaining whether it depends upon disease of a part.

The chief objection to specialities in medical practice is the danger that the doctor who treats but one part of the body may lose sight of the interdependence of diseases. This must always be a grave objection to very narrow specialities, but it does not apply to the broad division of the practice of medicine into Departments - that is to say, such a reasonable application of the principles of the "division of labour" as shall enable each practitioner, not only to completely master the department of Medicine which he selects for special study, but to advance the general knowledge of the profession by his investigations and experience.

For example, diseases of the ear are often dependent upon, or are connected with, diseases of other parts of the body; and the doctor who confines his practice to diseases of the ear may be in danger of losing sight of the broad facts of medicine, and in attempting to cure the ear may damage the body; but by extending his practice to all the organs of special sense, which might fairly form a department of Medicine, he would be obliged to take in a range of observation and thought which would enforce a knowledge of the interdependence of diseases.

Again - Diseases of the heart and arteries are intimately connected with those of the lungs and throat; diseases of the lungs with those of the heart, arteries, and windpipe; diseases of the brain with those of the lungs, heart, and arteries; and all of these are often inseparably connected, in the relation of cause or effect, with affections of the stomach, liver, pancreas, kidneys, intestinal glands, etc., etc. Therefore, for a doctor to limit his practice to diseases of the heart, to diseases of the throat, to diseases of the lungs, or to diseases of the windpipe, is to constitute a speciality so narrow that he is in danger of losing sight of the great principles of medicine. If, on the other hand, he selects for special study and practice such a broad department as Diseases of the Chest - that is to say, of all the respiratory and circulatory organs, and the associated processes of digestion and assimilation - he will be obliged to take in a range of observation and thought necessitating a constant remembrance of the interdependence of diseases, and he will be competent to deal with all classes of disease as well as those peculiar to his own department. I have instanced Diseases of the Chest because it is one of the most important "lines" of practice, and the one with which- I am most intimately associated; but the same remarks apply to Obstetrics, to Fevers, to the Diseases of Children and to other large divisions of medicine. Thus depart merits of medical practice may be wisely selected by different medical men for special study - but narrow specialities are dangerous and objectionable, unless those who confine themselves to them are content to act simply as the assistants of the more general physicians and surgeons, which is not likely to be the case. (See Part II., "On the interdependence and prevention of diseases and the diminution of their fatality.")

Diet is so little understood that, very often, those are the best off who abstain from all attempts to meddle with it, and are content to follow the dictates of their instinct. This, of course ought not to be the case, for diet, properly understood, may be made a powerful agent in the restoration and maintenance of health; and errors of diet are at all times capable of becoming serious causes of disease.

But, unfortunately, interference with diet, like all good things, is particularly open to abuse, for nothing is easier than to lay down a complicated code of restrictions and rules as to "what to eat, drink, and avoid," and the patient is very apt to think that the skill of the doctor increases with the number and variety of his orders. But those who understand the principles of diet know that the reverse is much nearer to the truth, and that learning and skill in dieting a patient are shown by the wisdom with which the doctor, instead of meddling with unimportant details, seizes upon the few essential points on which the vice or virtue of a diet will generally be found to turn. Thus, in a case of diabetes (See Diet for Diabetes, Chapter VI (Some Principles Of Diet In Disease).), the ignorant intermeddler may order fifty restrictions without doing his patient the slightest good; whereas, the doctor who understands the nature of the disease and the principles of diet, will speedily relieve his sufferings by telling him to take whatever he likes, so long as he touches nothing which contains starch or sugar. Thus, again, I have often seen patients suffering from acid dyspepsia who have been ordered and forbidden so many different articles of food that their lives were rendered miserable, without the slightest relief to their complaint, whereas, by forbidding them to take cheese and malt liquor - the chief factors of their malady - and allowing them to eat and drink whatever else they pleased, their sufferings have been speedily removed and their lives made enjoyable.