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PNEUMONIA. — The mortality rate from pneumonia was also comparatively uniform during the twenty-year period, the extremes being 12.4 per 10,000 in 1871, and 18.2 in 1888. There was an increase from 14.6 per 10,000 in the first ten years to 16.6 in the second ten years.

The effect of density upon the mortality from this disease does not appear to have been so decided as in the case of other well-known infectious diseases, the ratio being as 15.6 per 10,000 for the densely settled towns, and 14.1 for the sparsely settled. Geographical position, with reference to distance from the sea-coast, appears to have had a marked coincidence with the mortality rate, the inland counties presenting a high mortality rate and the sea-coast counties a low one. Elevation above the sea also appears to have coincided with a high mortality from this cause. With reference to these two conditions, distance from the sea-coast and elevation above sea level, consumption and pneumonia appear to be to a considerable degree complementary.

In connection with the foregoing summary the following condensed statistics are presented, which have reference to the relation of sex, age and season of the year to the diseases under consideration. They will be found useful in making a more complete study of the subject. In the table which relates to the mortality by months (page 873) the percentages have been reduced to uniform periods of one-twelfth of a year, in order the better to show the actual incidence of the disease at each such period.

In a very small number of cases the sex was unknown. The numbers were quite small, and are therefore disregarded in the foregoing tables. The following figures give the mortality by sex, the deaths of each sex from the given disease being compared with the persons living of each sex, and in the case of diseases peculiar to children the comparison is made with the persons living of each sex of ages from 0 to 10, and in the case of cholera infantum from 0 to 5.

In the first table on the following page the only diseases in which the difference in the mortality of the sexes is excessive and worthy of special notice are small-pox and phthisis. For every 1,000 males who died of small-pox there were 662 deaths of females. It is worthy of note, however, that the mortality of the sexes at different ages presented a wide variation. While the mortality of the two sexes for the period of life 0-20 years was exactly equal, or 50 per cent. of each, that of the remainder of life was 70.5 per cent. for males and 29.5 per cent. for females. It would appear that this remarkable result is due to the much greater exposure of males to infection in adult life, while that of children is practically equal; and not even the fact of a greater exposure of female operatives in the paper-making industry is sufficient to counterbalance the still greater exposure of males in other densely settled communities.

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Death Rates per 10,000 of the Population living at Each Age Period of Life

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The mortality for phthisis was in the ratio of 1,000 males to 1,202 females, or, when compared with the number living of each sex, as 1,000 males to 1,115 females. The mortality of the sexes also differed considerably at different ages, that of females being greatest for all ages up to 30 years, while that of males was greatest for all the later ages from 30 to 80 years.

In the table of age periods the most noteworthy departure from what may be termed a normal rate of increase or decrease from one age period to another exists in the column for small-pox. In the few instances of such tables as have been preserved in Europe from the statistics of the pre-vaccination period, the death rate from small-pox of children under 5 years was very much greater than that of the present day, while that of the later ages was comparatively small. In the present table for Massachusetts the large ratio of deaths of children under 5 years corresponds to the experience of partially vaccinated populations, and the increasing ratio at the ages 10-30 undoubtedly indicates a neglect of re-vaccination at a time when the renewed susceptibility to smallpox has not been met by re-vaccination of persons living at those ages.

Small-pox.

Fever.

Typhoid

Cholera
Infantum.

tion. Consump

Pneumonia.

Scarlet

fever.

Diphtheria and Croup

Small-pox.

Fever.

Typhoid

Cholera

Infantum.

Phthisis.

Pneumo

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SEASONAL MORTALITY.

[See diagram on the following page.]

Percentages of Deaths in Different Months of the Year (1871-90).

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The following table affords a good illustration of the truth of Dr. Farr's rule or statement, relative to the effect of density of population in increasing the death rate from infectious diseases. In the direction westward toward Berkshire County the same uniformity is not shown, since the diminishing ratio of density is not maintained in that direction, Hampden having a greater density than Worcester County. In the southward direction, however, as shown in the following table, the mortality rate from two of the principal infectious diseases decreases inversely with the distance from the metropolitan county of Suffolk and the density of population (expressed in acres per inhabitant):

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Small-pox.

Typhoid

Fever.

Cholera

Infantum.

Consump

tion.

Pneumonia.

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The diagrams shown above are intended to illustrate the seasonal mortality from the eight causes of death presented on page 873. In the construction of these diagrams, the radius of the circle represents the average mortality of one month. The actual mortality of each month is represented relatively by the distance of the points or angles of the shaded areas from the centre of the circle. The shaded areas do not express the actual mortality quantitatively.

The total numbers of deaths from which the diagrams are constructed are stated on page 760.

PNEUMONIA.

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HEALTH OF TOWNS.

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