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remedial agents. It will designate the localities where disease is most rife, and where there is the most tendency to particular classes of sickness and infirmity.”

The value of the following study consists mainly in the light which may possibly be thrown upon the study of the causes of disease. A thorough knowledge of the natural history of infectious diseases, including their etiology, is essential to an understanding of the methods to be adopted for their prevention.

Dr. Haviland says upon this point : “ It is for this reason that I look upon the investigation connected with the geographical distribution of disease as essential to a practical knowledge of preventive medicine ; for it involves the study of the physical, geological, meteorological •and other natural and social characters of the country or district, the diseases of which are the subject of inquiry.”

Allowance must be made in the following paper for the fact that all medical statistics based upon the returns of causes of death are only as trustworthy as medical diagnosis can make them. The following table, from the registration report of 1890, shows, however, that a progressive improvement has taken place in this direction, and that the number of deaths from “unknown or unspecified causes” has gradually diminished in the past twenty years.

Deaths from Unknown or Unspecified Causes, and Percentages,

1871-1890 (20 Years).

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Average (1871-1880),

3.21

Average (1881-1890),

1.37

Another point which should be borne in mind is the danger of making deductions from small populations, in which a very slight increase or decrease in the number of deaths from any disease has a violent effect upon the mortality rate of such population. In the study of small-pox, for example, the difference between one and two deaths from this cause in any one of the small towns changes its position from a rank below the average to an excessively high position, and far above the average. Hence the principal conclusions in this paper will be taken from large groupings, and not from the extremely small populations of the towns in rural districts.

The compiler recognizes that any statistician may have personal and peculiar views in regard to subjects which he may be called upon to treat, which may bias his mind in the interpretation of statistics whenever doubt arises. The primary requisite, as Dr. Longstaff says, in the treatment of statistics, is a logical mind and a sound logical training, and, secondly, a good general knowledge of his subject.

The number of municipalities having a city government at the beginning of the period (1871–90) was 14, and the number having such form of government at the close of the period was 28. Those having town governments at the beginning of the period were 322, and at the close 318.

A few changes have been made in the dividing lines of towns, for which due allowance has been made, where the changes included territory containing a considerable number of inhabitants; and a few new towns have been incorporated.

Arbitrary methods must necessarily be taken for expressing the ratios of mortality upon the map, and in many instances towns occupying an area of fifty or even one hundred square miles of surface may have a rural population of one, two or three thousand inhabitants, occupying but a small portion of this area.

The population used as a basis for calculating the ratios of mortality is that of 1880 (U. S. census), which is taken as an average of the whole period of twenty years. This would be sufficiently correct for all towns in which the rate of increase was uniform for the whole period of twenty years.

For a considerable number of the cities and towns, however, the increase in the second decade was much greater than that of the first. For these towns, about one-fourth of the whole number, a re-estimate was made and an average taken of the population by five census enumerations, 1870, '75, '80, '85 and '90. In many of the farming towns the population was quite stationary and in some there was a decrease.

In considering the different parts of the State with reference to the comparative prevalence of different diseases, the county has been selected as a large sanitary district. It is evident, however, that such divisions have but little significance for the purpose of sanitary study.

For example, Franklin, Hampshire and Hampden counties have quite similar characteristics in their equal distance from the sea, in forming the principal drainage basin of that part of the Connecticut River which traverses the State, and in other characteristics. They might therefore be treated as one group.

For the purpose of making a more intelligent classification I have therefore classified the towns into two general divisions of manufacturing or densely settled towns, and agricultural or sparsely settled towns.

The former embraces 87 municipalities, including all the 28 cities. None of this number had less than 2,000 inhabitants in each, and only ten had less than 4,000; and each of these smaller towns had one or more villages having a comparatively dense population, living in a district of limited size. The average population of each municipality in this group by the census of 1880 was 15,434. Most of them have a steadily increasing population, a large portion of which consists of immigrants, either of European nativity or from the British North American provinces. In many of the towns of this class there is a rural population of considerable size living in those portions outside the more densely settled villages. The actual increase in population in the rural towns, for the period of twenty years, between the census of 1870 and that of 1890, a period nearly coincident with that under consideration, was 111 per cent., while that of the larger or manufacturing and urban districts was 70 per cent.

The other group, of agricultural towns, 259 in number, has but few towns having 3,000 in each, and the average population of each in 1880 was 1,700. Their population is distributed over an average area of nearly thirty square miles for each township. The principal occupation of the people of these towns consists of dairy farming, market gardening, and other branches of agriculture. A few of these towns are summer resorts, either upon the sea-coast or in the inland region. Some of the towns of this general class have increased slightly in population in the past twenty-five years, many have remained stationary and a considerable number have slowly decreased.

I have included Provincetown and Nantucket in the former class, neither of which is a manufacturing town; but each has a comparatively dense population living in a small area, and a considerable area of nearly unoccupied sandy territory lying outside the densely settled seaport. Both towns are exposed to sea breezes throughout the year.

Newton is neither a manufacturing nor a densely settled municipality, but a suburban residential city, with a population consisting mainly of wealthy or comparatively well-to-do inhabitants.

The population of the first group in 1880 was 1,342,782, and that of the second group 440,303. Tables are presented giving the comparative rank of each town for each one of the eight causes of death considered in this paper, together with maps in which the degree of mortality is presented in five grades, as follows:

1. Towns in which there were no deaths from the disease in question.

2. Towns in which the mortality was more than fifty* per cent. below that of the State.

3. Towns in which the mortality was below that of the State, but not fifty* per cent, below it.

4. Towns in which the mortality was above that of the State, but not fifty* per cent. above it.

5. Towns in which the mortality was more than fifty* per cent, above that of the State.

Even these smaller sub-divisions (the towns) do not convey the exact relation of the mortality rate from any particular disease, since the broad patches of color shown upon the maps

* In the table of general death rates the dividing limits of the groups are placed for the sake of convenience at 15 per cent. instead of 50 per cent.

convey to the eye an impression of quantity in proportion to their areas, while the actual prevalence in towns of small population and large area was in most cases confined to some densely settled village occupying but a small portion of the colored

al'ea.

For example, under the head of measles, the neighboring places Fall River and Freetown in Bristol County have a nearly equal area, and the coloring expresses to the eye a similar ratio of mortality to the population only; but the actual number of the population is more than fifty times greater in Fall River than it is in Freetown.

It would have been a very important and valuable addition to this inquiry if the prevalence of sickness from the same causes, independent of mortality, could have been presented. No extended and complete inquiry of this character has been undertaken in the State since the limited inquiry of the Massachusetts Medical Society in 1858 and 1859, and that of the State Board of Health in 1874 ; consequently we must trust to the information contained in the registration reports, which present only the data of mortality.

The writer has found valuable assistance in the following published reports :

Dr. Bowditch's well-known report to the Massachusetts Medical Society in 1862, upon consumption in Massachusetts.

Dr. Geo. Derby's papers upon consumption in the Twentyfourth Registration Report of Massachusetts, 1865, and typhoid fever in the second report of the State Board of Health, 1871.

Dr. C. F. Folsom's statistical tables upon diphtheria in the Thirty-ninth Registration Report of Massachusetts, 1880, and upon typhoid fever in the Fortieth Registration Report, 1881.

A study of phthisis and pneumonia in Massachusetts, statistical and climatological, by W. E. Smith, M.D., 1888.

The etiology and treatment of the summer diarrhea of infants, by Dr. H. C. Haven, Boston, 1886.

Also in the valuable English reports of Dr. Haviland upon the geographical distribution of certain diseases in Great Britain, 1875, and in the excellent work of Dr. Longstaff, entitled “ Statistical Studies," 1891.

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