1. _City Populations have a Larger per Cent of Females than Rural Populations._ All of our fifteen largest cities, except three, contain a larger per cent of females than the states in which they are located. Thus New York state has 50.37 per cent of its population female; New York city, 50.56 per cent; Pennsylvania, 49.29 per cent of its population female; Philadelphia, 51.18 per cent; Missouri, 48.38 per cent of its population female; St. Louis, 49.51 per cent. In towns of the United States of more than 2500 population the per cent of females is 50.03, while the rural districts of the United States have only 48.08 per cent of their population female. The cause of this is perhaps to be found in the fact that in cities there is always a larger infantile mortality among males than among females, and that in towns there is a larger proportion of female children born than in the rural districts. 2. _People in the Active Period of Life, from Fifteen to Sixty-five Years of Age, predominate in the City_. According to Dr. Weber, out of every 1000 individuals in the United States as a whole there are 355 under fifteen years of age, 603 between fifteen and sixty-five, and 29 above sixty-five years of age. But in the great cities there are only 299 under fifteen years of age, and only 29 above sixty-five years of age, while 668 are of the age between fifteen and sixty-five years. (In both cases the age of three in a thousand was unknown.) The cause of the predominance of those in the active period of life is undoubtedly due to the immigration into the cities from the country districts. This makes the life of cities more energetic and active, more strenuous than it would otherwise be. 3. _The Great Cities in the United States have over twice as many Foreign-born in their Population as the United States as a whole_. This has been sufficiently discussed under the head of immigration. 4. _The Birth Rate is higher in the Cities than in the Rural Districts._ This is primarily due to there being more women of child-bearing age in the cities. In the United States it is also due to the presence of so many foreign-born in the cities. The marriage rate is also higher in the cities than in the rural districts. The following statistics based on a thousand population show the relative difference between the cities and the rural districts of the New England States in marriage rate, birth rate, and death rate for 1894-95: Marriage Rate Birth Rate Death Rate Boston........................ 23.10 31.24 23.23 Cities over 50,000............ 18.89 29.72 19.49 Rural Districts............... 13.77 21.76 17.38 5. _The Death Rate in Cities is also higher than in the Rural Districts_, as the above table has just shown. This is undoubtedly due to the poor sanitary and living conditions of large cities.