The foregoing data show the relative importance of the different classes of disease as causes of premature death, and of the particular diseases giving rise to the greatest mortality in the larger number of the classes. The data are given as to the classes of disease with reference to the population at all ages under seventy-five years; and as to particular diseases, with reference to the population at all ages, as if the mortality from the various diseases were distributed equally among the people within the period of life designated. It must now be understood. that the mortality from the several diseases and classes of disease falls with very different force at various periods of life. There is a wide difference between the incidence of the several causes of death in infancy, in childhood, in youth, in mature age, and in the decline of life.

In infancy diseases of the brain and nervous system, notably, convulsions, rank first among the causes of death, diseases of the lungs have the second place, and diarrheal diseases the third.

From the end of the first year of life to the end of the

fifth-that is to say in early childhood-the infectious diseases, especially scarlet fever and whooping-cough, give rise to the greatest mortality; then, as in infancy, next in order of mortality, at this period of life, come lung diseases, and third, the diarrheal diseases.

In childhood and early youth (five to fifteen years) the infectious diseases are the chief causes of mortality, principally scarlet fever and continued fevers.

From youth to manhood (fifteen to twenty-five years) phthisis is the most important cause of death, and the infectious diseases sink to the second place.

In early manhood (twenty-five to thirty-five years) phthisis still maintains the first rank among the causes of death, but a marked increase in mortality is now observed from other diseases of the lungs. The infectious diseases continue to hold the second rank among the causes of death at this period of life.

In manhood and maturity (thirty-five to fifty-five years) phthisis maintains its predominance among the causes of death, but now the mortality from other diseases of the lungs becomes largely augmented. The second place in the order of causes of death at this period of life is taken by diseases of local origin, especially local affections of the brain and nervous system, of the heart and bloodvessels, and of the digestive organs; cancer now becomes an important source of mortality; but the infectious

diseases sink to a comparatively low place among the causes of death.

In the decline of life (fifty-five to seventy-five years), the diseases of local origin, including diseases of the lungs, are the chief causes of death, phthisis, the infectious diseases and general diseases, as a rule, except cancer, becoming relatively less predominant. At this period of life, indeed, the causes of death foreshadow the more general decay of old age (seventy-five and upwards), where death, if it does not arise from the natural inability of the several organs, in the progress of decay, to continue their functions, unaffected by exterior circumstances, is mainly brought about by local accidents of the brain and nervous system, the heart and blood-vessels, irredeemably damaged in the course of the decay.

The progress of fatal disease through the several periods of life has, in fact, characteristic relations with the natural condition of the body at the different periods. The fatal diseases of infancy are significant of the immaturity and mobility of the infants' organs and functions. The fatal diseases of childhood relate, not so much to states of the system then in fullest vigour of vital reaction (to inherent conditions of the body, so to speak), and to the influence of the media in which we live, as to the accidental liability of exposure to morbific agencies current among populations, such as the contagions of the

catching diseases, as, for example, scarlet-fever, smallpox, measles, typhus, &c. With the completion of manhood, diseases indicative of local degenerations of tissue begin to be predominant, and with each successive stage of life this predominance becomes more marked. In old age the degenerative changes, which at earlier periods of life are regarded as the signs of disease, now appear as the natural consequences of decay, and death becomes a physiological, not a pathological fact-as the termination of a natural life, not as the premature close of a life cut short by disease.

CHAPTER III.

THE CONDITIONS UNDER WHICH THE CAUSES OF
PREMATURE DEATH OPERATE.

We now come to the consideration of the conditions under which the causes of premature death operate.

And, first, let it be observed that these causes operate with very different degrees of intensity in different parts of the kingdom. Thus while in their totality they kill the population inhabiting the agricultural districts south of London at a rate of about 1,500 annually in every 100,000 living, they kill the population of certain manufacturing

and mining districts at rates of about 2,200 (Merthyr Tydvil), 2,500 (Newcastle-on-Tyne), 2,700 (Leeds), and 3,400 (Liverpool). The wide range of intensity of operation of these causes in different localities when regarded as a whole is, as might be inferred and will presently be shown, even more markedly observed in regard to the distribution in various localities of the particular diseases or class of diseases which contribute most to swell the number of premature deaths. The study of the circumstances under which the difference of prevalence of these diseases in different districts occurs, furnishes the clue to the conditions under which the causes of premature death operate.

And here it may be well, before entering upon an examination of the conditions of prevalence of the several classes of disease which have been set forth as causes of premature death, to interpose a caution as to districts in which the rate of premature mortality is least. It has become customary to speak of these districts as healthy districts, and the Registrar-General has adopted (if, indeed, he did not first use) this term with regard to them. The phrase is eminently misleading and, indeed, mischievous. The term healthy as applied to these districts is in reality used relatively with regard to the greater mortality of other districts. It will scarcely be maintained that people live too long in these so-called healthy districts, or that