The Prolongation of Life: Optimistic Studies

by Elie Metchnikoff

Hygienic measures have been the most successful in prolonging life and in lessening the ills of old age.

Although until quite recently hygiene has rested upon a very small number of scientifically established facts, and although its precepts have not been followed rigidly, none the less it has already succeeded in increasing the duration of human life. This becomes evident if we compare the mortality tables of the present day with those of the past.

There is reason to state definitely that the mortality in civilised countries has decreased on the whole in the last one or two centuries. I have taken some facts regarding this from the valuable monograph of M. Westergaard.[114] That author came to the conclusion that the mortality rate in the 19th century in civilised countries was “much lower than in most earlier centuries.” This diminution has been chiefly in infantile mortality. According to Mallet, the mortality rate of infants in the first year of their life was, in Geneva, 26 per cent. in the 16th century, and fell gradually to 16-1/2 per cent. at the beginning of the 19th century. A similar change has been reported from Berlin, Holland, Denmark and other places. However, it is not only very young infants that have shown a diminution in the death-rate. The life of old people has been prolonged to an extent equally remarkable. The following are some of the facts which support this statement. Whilst the old Protestant clergymen of Denmark at ages varying from 74-1/2 to 89-1/2 years had a mortality rate of 22 per cent. in the second half of the 18th century, the rate had sunk to 16·4 per cent. by the middle of the 19th century. This is not an isolated fact. The old clergymen of England (65 to 95 years) have also come to live longer, because in the 18th century the mortality rate was 11·5 per cent. and in the 19th century (1800-1860) only 10·8 per cent. There has been a similar decrease in the mortality rate in the members of both sexes of the Royal Houses of Europe (Westergaard, p. 284).

From 1841 to 1850, in England and Wales 162·81 individuals out of every thousand of both sexes died annually, but the corresponding figure for the period 1881 to 1890 was decreased to 153·67 per thousand.

Westergaard (p. 296) has displayed in a most useful table the mortality in the chief countries of Europe and in the State of Massachusetts, in two periods of time. In the case of old persons from 70 to 75 years, there has been a constant decrease in the death-rate, without any exceptions. The exact statistics collected by Pension Bureaus and Life Assurance Companies exhibit the same general tendency.

It cannot be disputed then that there has been a general increase in the duration of life, and that old people live longer at the present time than in former ages. This fact, however, cannot be taken absolutely, and it is still possible that in particular cases there may have been more centenarians hitherto than at present.

The prolongation of life which has come to pass in recent centuries must certainly be attributed to the advance of hygiene. The general measures for the preservation of health, although they were not specially directed to old people, have had an effect of increasing their longevity. As in the 18th century and for the greater part of the 19th, the science of hygiene was in a very rudimentary condition, we may well believe that improvement in cleanliness and in the general conditions have contributed largely to the prolongation of life. It is now a long time since Liebig said that the amount of soap used could be taken as a measure of the degree of civilisation of a people. As a matter of fact, cleanliness of the body brought about in the most simple way, by washing with soap, has had a most important effect in lessening disease and mortality from disease. In this connection, the fact recently published by Prof. Czerny,[115] a well-known German surgeon, has a special interest. Although cancer, the special scourge of old age, has increased in recent times, one form of the disease, cancer of the skin, has diminished notably. “Cancers of the skin,” Prof. Czerny says, “are met with almost exclusively on uncovered regions of the body, or on parts accessible to the hands. They develop especially where the susceptibility is increased by ulcers or scars which are easily soiled. And so it happens that in the classes where care is taken as to cleanliness cancer of the skin is very rare and certainly much more rare than it used to be.”

M. Westergaard thinks that vaccination against small-pox has been of considerable importance in lowering the death-rate in the 19th century. This, however, can have had little effect on the duration of life in old people, as deaths due to small-pox in the old are excessively rare. For instance, in the second half of the 18th century, that is to say before the introduction of Jenner’s method, the mortality from small-pox at Berlin was 9·8 per cent. of all the deaths, but of these only 0·6 per cent. were cases of persons more than fifteen years old. The rest, that is to say, 99·3 per cent. fell on children under that age. It may be supposed that most of the old people at that time were already protected by previous attacks of small-pox, contracted when they were young.

If hygiene were able to prolong life when it was little developed, as was the case until recently, we may well believe that, with our greater knowledge of to-day, a much better result will be obtained.