Medical evidence has in the past generally asserted a correlation of health to density. A comparative study of figures from 71 cities in the United States brought out other interesting facts. Mortality rates were plotted against acreage of parks per 1000 persons, the mileage of water and sewer pipes per 1000 persons, and the area of acreage of parks and streets, and the mileage of streets, with these results:

Park area per 1000 persons apparently does not affect the mortality rate, for there is no indication that the mortality rate falls with increased park area.

There appears however to be a relation between mortality rates and sewer and water-pipe mileage. The mortality rate falls as the per capita mileage of water and sewer pipe increases.

The mortality rate falls as the total acreage of streets and parks increases, though it does not vary directly with the presence or absence of parks.

It seems fair to assume, therefore, that the distances separating buildings as shown by the ratios between mileage of water pipe, mileage of sewers, acres of streets and the mortality rate, do affect the mortality rate.