laundry purposes, and the stinking vault still maintains its position in the back yard. Observe this fact also: a considerable majority of the population of New Haven resides upon the sewered streets, and yet only nine out of forty-three deaths from a disease which is chiefly caused by foul air occur among the majority; while thirty-four of the forty-three are among the minority, who reside in dwellings surrounded by the fragrant companionship of time-honored filth-pits. Any person can draw intelligent inference from the above plain facts."
The remaining important factor in the production of infantile diarrhœa is overcrowding. This, indeed, is but the occasion of one of the most dangerous forms of filth, in the shape of air deprived of its vitalizing qualities, and charged with impurities derived from the breath and bodies of men and animals, which is sometimes known as "crowd-poison." "It is this air," says Dr. Richardson, "in our overcrowded towns and cities, where there is no vegetation to revivify it, which we distinguish as something so different from the fresh country air that streams over meadow and forest. It is the breathing of this air that makes the child of the town so pale and lax and feeble, as compared with the child of the country. It is this air that renders the atmosphere of the crowded hospital so deficient in sustaining power. It is this air that gives to many of our public institutions, in which large masses of our poorer, ill-clad, uncleansed masses are herded together, that 'poor-smell,' as it is called, which is so depressing both to the senses and to the animal power."
Cholera infantum is well known to be almost exclusively a disease of cities, and absolutely so in its epidemic form. The city of Manchester, N. H., contains only about one tenth of the population of the State, yet in 1883 it furnished nearly one half of the whole number of deaths from this disease; while in 1885, the three cities of Dover, Portsmouth, and Manchester, together containing less than one sixth of the whole population, reported considerably more than one half of the entire mortality from cholera infantum. The State of Massachusetts contains eighteen cities and towns of more than fifteen thousand inhabitants, while Vermont has none. The mortality from cholera infantum in 1883 was 3·49 per 10,000 in Vermont, and 9·53 per 10,000 in Massachusetts.
According to Dr. Farr, the mortality of districts increases with the density of their population; not, however, in the direct proportion of their densities, but as the sixth root of their densities. But while the total mortality increases in this proportion, the mortality imder five increases in a much greater ratio. Thus, with a density of 166 to a square mile, the death-rate at all ages is 16·94 per 1,000, while of those under five it is 37·8 per 1,000. This ratio increases gradually and with considerable regularity
