Books are difficult of disinfection. Steam damages leather. The penetrating power of dry heat is doubtful. Cheap books should be burnt. Abel discovered virulent diphtheria bacilli on toys six months after the patient, to whom they belonged, had diphtheria. Formalin and phenol vapours have been used to disinfect books in closed chambers, the books being stood on end. Letters can be rendered safe by steam disinfection.
Corpses of infectious patients should be placed in the coffin and buried as early as possible. A thick layer of sawdust saturated with lysol or cresol should be placed at the bottom of the coffin, and the corpse enveloped in cotton wool. Cremation is better than burial.
[CHAPTER XLVIII.]
VITAL STATISTICS.
Vital Statistics is the science of numbers applied to the life-history of communities. Its significance is similar to that of the more recently coined word—Demography—though the latter does not necessarily confine itself strictly to study of life by statistical means. Another term has been frequently used in recent years—“Vital and Mortal Statistics.” The continued use of the word “mortal” in this connection is undesirable and objectionable. The term “Vital Statistics” is comprehensive and complete, as death is but the last act of life.
Of the problems of life with which the science of Vital Statistics is concerned, population, births, marriages, sickness, and deaths, possess the chief importance; and in the following sketch of the subject I shall concern myself chiefly with these. The subject naturally divides itself into two sections: the sources of information, and the information derived from these sources, and both of these will require consideration.
The importance of numerical standards of comparison in science increases with every increase of knowledge. The value of experience, founded on an accumulation of individual facts, varies greatly according to the character of the observer. As Dr. Guy has put it: “The sometimes of the cautious is the often of the sanguine, the always of the empiric, and the never of the sceptic; while the numbers 1, 10, 100, and 100,000 have but one meaning for all mankind.” Hence the importance of an exact numerical statement of facts. The sneering statement that statistics cannot be made to prove anything can only be made by one ignorant of science. In fact, nothing can be proved without their aid, though they may be so ignorantly or unscrupulously manipulated as to appear to prove what is untrue. Instances of fallacious use of figures will be given as we proceed.
An accurate statement of population forms the natural basis of all vital statistics. Thus the comparison of the number of deaths in one with the number of deaths in a second community has no significance unless we know also the number living out of which these deaths occurred. Even then our knowledge would be defective, without further particulars as to the proportion in each population living at different ages, and the number dying at the corresponding ages. For other purposes we should require to know the number married and unmarried, the number engaged in different industries, and so on; in order that the influence of marital conditions, of occupation, etc., on the prospects of life may be calculated. The first desideratum of accurate vital statistics is a census enumeration of the population at such intervals as will not cause the intervening estimates of population to be very wide of the mark. In this country a decennial census is taken, the last occurring in 1901. In the intervals the population of the entire country, and of each town or district is estimated. Various methods of estimating the population have been adopted. (1) If a strict record of emigration and immigration is kept, then in a country in which a complete registration of births and deaths is enforced, the population can be easily ascertained by balancing the natural increase by excess of births over deaths, and the increase or decrease due to migration. This is done in New Zealand, but is impracticable in England, as no complete account of migration can be kept.
(2) The increase of inhabited houses in a district being known year by year, the increase of population may be estimated on the assumption that the number of persons per house is the same as at the last census. This may not be strictly accurate. In 1901 it was found that in England and Wales the average number of persons per house was fractionally less than in 1891.
(3) It may be assumed that the annual increase during the present decennium will be 1 ∕ 10 of the increase during the last decennium 1891-1901. If so, the population, e.g. in 1905, is the enumerated population in 1901 plus 4¼; times the annual increase occurring during 1881-91. (The fourth is required because the census is taken early in April, and the population is estimated to the middle of the year). This method is fallacious, because it makes no allowances for the steadily increasing numbers who year by year attain marriageable age and become parents. It assumes, in other words, simple interest, when compound interest is in operation.