Zoning is an essential part of city planning. Generally speaking, about three-fourths of the land area of a city is privately owned and subdivided into blocks and lots; the other fourth, devoted to streets, parks, etc., is owned by the municipality or dedicated to public uses. Again, speaking in generalities, municipal control of the public land is obtained through the governmental power of eminent domain, while municipal control over the use of private property is dependent on the exercise of police power. With rare exceptions, eminent domain has nothing to do with zoning; there is no question of compensation to the owner; no question of the necessity of acquiring private property for public use. The constitutionality of zoning depends on whether the restrictions proposed are justifiable under a reasonable use of the police power, a common-law principle which, although undefined and undefinable, finds its backing in certain well-recognized needs of the community. Used conservatively the police power has to do only with injury to health, safety, or morals; used more liberally it covers, in addition, such matters as the public order and convenience and even extends to what are called the "amenities of ife." With the increasing concentration of people in cities, there is good reason for the widening scope of the police power which has been witnessed during recent years.

1 Paper presented at the City Planning Division of the American Society of Civil Engineers, Detroit, Mich., October 24, 1924.

2 Before Mr. Whipple's death he served as professor of sanitary engineering of Harvard University.

Zoning is advantageous to a city in many ways. It tends to stabilize real-estate values, to promote orderly building, to enhance beauty, and to develop local self-consciousness and civic responsibility on the part of the people. Yet, in the face of these benefits, zoning is likely to be declared by the highest courts to be unconstitutional if it cannot be justified under the police power; and although instances may be cited where the police power has been exercised in a constructive manner to promote the general welfare of a community, its preponderant use has been to prevent injury to health, safety, morals, and - the lawyers like to add - "the like." The purpose of this paper is to outline the scientific evidence bearing on the relation of zoning to health.1

Health

At the outset it is important to grasp the full meaning of the word "health," to realize that it is more than the absence of disease; that it has a positive quality; and that it has to do with the mind as well as the physical body. It is useful to keep in mind the derivation of the word from the Anglo-Saxon "haelth," which implied wholeness. If one were to venture a definition, it might be said that health is "that state of quality of life in which the body is sound, the various organs function naturally, and the whole organism responds adequately to its environment."

In a popular sense public health means the general or collective health of the community. In an administrative or legal sense it means the health of the community as influenced by factors which affect a considerable number of people in some connected way. The police power is not limited to public health used in this restricted sense, but deals with health. Attention should be called to the fact that the adjective "public" restricts the word "health" instead of amplifying it.

Although it is difficult to define normal health, it is recognized that some factors tend to injure it, or lower its state, whereas other factors tend to promote it, or raise its state above the normal. Normal health presupposes a normal environment, the two ideas being complementary and inseparable. It is the purpose of zoning, as it is that of sanitation, to secure and maintain an environment in which normal human beings can lead normally healthful lives.

1 [Since this paper was written the U.S. Supreme Court handed down a decision (Euclid village case, November 22, 1926) which was a victory for zoning. The Court upheld the constitutionality of excluding stores from residence districts, factories from business districts, and apartment houses from detached-house districts.]

In an address on "Sanitation - Its Relation to Health and Life" before the Sanitary Engineering Division of the Society, the writer pointed out that the principal injurious factors to health are infections, poisons, and accidents. The physiological factors air, food, water, light, temperature and humidity, sleep, exercise, clothing, and shelter, and the sensatory factors smell, taste, sound, sight, and touch, are either health promotive or health injurious, according to their nature. This classification, indefinite though it is, serves to steady one's ideas when considering the complicated relations between health and environment.

Quantitatively, health can be measured only imperfectly and in part. Individual health may be expressed in terms of growth, height, weight, and other biometrical units. Community health on its negative side may be measured in terms of death rates and sickness rates, general and specific, for different classes, age groups, and particular diseases. No adequate methods of measuring community health, on its positive side, have yet been developed; perhaps they will come in time.

To a large extent, therefore, the subject under discussion is beyond the range of statistics; and reliance must be placed on accumulated experience and the opinions of competent authorities, rather than on logical scientific demonstration, although, in certain parts of the problem, scientific proof is available.