is expectation of life at that age, as taken from life tables, added to the age. Probable Duration of Life. The probable duration of life is the age at which a given number of children born at the same time will be reduced to half the number. Expectation of Life.—The expectation of life is the average length of time a person of any age may be expected to live. This is computed from life tables. The following life table gives the results of computations from the mortality returns in England and America, and the results of the experiences of life insurance companies: Age. Males. Females. Males. Females. Males. Females. Males. Females. Males. Females. o yr. 41.35 50.73 52.81 4 51.01 53.20 51.61 53.77 35 40 050 32.10 34.41 25.30 27.46 50.87 53.08 48.16 59.32 49.99 48.05 25.59 27.68 28.48 28.48 52.93 53.00 69.72 63.73 52.78 52.88 69.36 63 20 49.92 50.04 65.99 59.84 61.75 55.39 57.44 59.93 53.24 46.65 49.22 42.62 44.74 38 47 34.31 22.30 In order to construct such a table, we must know the number of persons living, their ages, the number of deaths, and the ages at death, and changes in population caused by unusual birth-rate, by emigration, immigration, and other causes. The expectation of life of females is greater than that of males according to the results obtained in England and in Massachusetts. The reverse is the case with the Jews of the United States. In the experience of the thirty life insurance companies of America the expectation of life of males is greater than that of females. This most interesting result obtained from the selected lives of the insured is difficult to explain. The relatively greater number of males insured may explain this difference in the result. The results obtained in England and Massachusetts indicate that the female mortality is lower than the male mortality, and it is evident, therefore, that the dangers connected with childbearing do not prevent the general female mortality at childbearing ages from being lower than that of males. The causes of the higher mortality among males are largely connected with the greater hardships and dangers connected with their occupations. In spite of the dangers of childbirth, married women have a much lower mortality than spinsters or widows. Widows of twenty to twenty-five years of age have a higher mortality than bachelors and married men of the same age. The expectation of life after the first year increases up to the fourth year, and remains higher than at the first year up to about the seventeenth year. Willich gives the following formula for the approximate calculation of the expectation of life at any age: Expectation of life = (So- a) = x, where, a the present age, and x = the expectation of life. Thus at forty years, X (So 40) = 26.66 years. Relation of Density of Population to the Deathrate. The relation of the density of the population to the death-rate is most important. Dr. Farr found that the mortality increases with the density of the population, but not in direct proportion to the density, but as its sixth root. Thus if D and D' density of the population in two places, and M and M' the mortality, then M' M D' The death-rate in each locality is, however, ND. influenced by other factors than the mere fact of the existence of a certain number of persons in a specified area. The most important factors which influence the death-rate under all conditions are the proportion which the infant population bears to the whole, or, in other words, the average age of the population, the nature of the occupation of the people, and, above all, the general sanitary conditions of the surroundings. Necessity of System of Notification.-Vital statistics cannot be obtained without some system of notification. Various objections have been raised against the notification of infectious diseases. The objection is frequently made that the friends of the patient wish to keep the matter secret, and that notification is a betrayal of confidence. There is usually delay in calling a physician, and this gives opportunity for the spread of the disease. The physician must be held responsible for reporting infectious diseases, otherwise the certainty of prompt notification is limited. The physician should be compensated for this extra work, though this is rarely done, and physicians should feel it a privilege to make the notifications, because it is the right of only those who are authorized to practise in a locality. It is, therefore, one mode of protecting the registered physicians against the invasion of those who are not qualified. The notification of infectious diseases frequently causes great discomfort and pecuniary loss to those who are isolated in the infected area. It interferes with the liberty and comfort of a large number of people, though this discomfort is insignificant to the general discomfort and loss entailed by general epidemics. Dr. Biddle, in a paper read before the Seventh International Congress of Hygiene, on "Should Compulsory Notification be made General?" gives the mean deathrates per 1000 living in twenty towns of England: Notification has been in force since the adoption of the Public Health Act of 1875. While there was a decline in the death-rate from all causes from 1871-75 to 1886-90 of only 14.5 per cent., there was a decline of 39.2 per cent. in the death-rate from the total zymotic diseases, and a decline of 64 per cent. in the death-rate from the notifiable diseases during the same period, showing the great value of notification in infectious diseases. Hospital for Infectious Diseases.--Where satisfactory isolation is impracticable the city should provide special hospitals for infectious diseases. This arrangement lessens the hardships of isolation, and may be instrumental, under proper regulations, in favoring the system of notification. The special need of pay hospitals for infectious diseases. has long been felt. Even where the patient could be satisfactorily isolated and treated in the home, there is a feeling that the pecuniary loss and inconvenience of house quarantine are much greater than the expense of hospital treatment. Consequently those that are able and willing to pay for hospital treatment cannot be accommodated anywhere except at the municipal hospital, and there is frequently objection to going to a public institution. It is safe to state that the time is not far distant when every large city will have pay hospitals for the reception of cases of infectious diseases. Such hospital treatment would overcome the obnoxious house quarantine practised to-day, at least as far as those are concerned whose time is most valuable from their business associations. APPENDIX. Rules for interchange of different expressions of results of analysis: To convert parts per 100,000 into grains per gallon = parts per 70,000), multiply by 0.7. To convert grains per gallon into parts per 100,000, divide by 0.7. To convert parts per million, or milligrams per liter, into grains per gallon, multiply by 0.07. To convert grains per gallon into parts per million, or milligrams per liter, divide by 0.07. To convert nitrogen as nitrates into nitric anhydrid, multiply by 108 and divide by 14. To convert nitric anhydrid into nitrogen as nitrates. multiply by 14 and divide by 108. To convert nitrogen as nitrites into nitrous anhydrid, multiply by 76 and divide by 14. To convert nitrous anhydrid into nitrogen as nitrites, multiply by 14 and divide by 76. To convert free or albuminoid ammonia into parts of nitrogen as ammonia, multiply by 14 and divide by 17. To convert nitrogen as ammonia into free or albuminoid ammonia, multiply by 17 and divide by 14. Rules for the conversion of degrees of one thermometer scale into those of another: Centigrade into Fahrenheit, multiply by 9, divide by 5, and add 32. Fahrenheit into centigrade, divide by 9, multiply by 5, and deduct 32. 31 481 |