rich, the poor, the dweller in cities and in the country, differing so much from each other in some respects, all resemble each other in having the same allotment, the same interval of time to pass from birth to death; that the variations of race, climate, food, conveniences, have nothing to do with the duration of life, we shall discover that the duration of life does not depend on habits, customs, nor on the quality of food. Nothing can change the physical laws which regulate the number of our years.'1 Buffon does not bring forward adequate data to support his statements, and we cannot admit the truth of his assertion in its entirety. But we have seen reason to believe that hereditarily the power of life in all men (within a few generations) is the same, disease, habits, and customs being dependent on external conditions, and thus longevity is rendered subject to external rather than internal causes, in the case of man; though with these varying external conditions are correlated small structural variations, which may make the longevity, in a certain sense, appear to be dependent on structure, so intimately bound up, so closely corresponding and reciprocal are structure and habit, even when dominated by such an organ as man's brain.

What we are concerned with, then, in the various kinds of man, is not variation in hereditary longevity,

1 Vol. ii. p. 76, quoted by Flourens, p. 52.

but variation in the longevity of groups characterized by different habits, food, &c., and it is not to the race of men, but to the difference of conditions in which they live, that we must direct our attention. As was stated above, man's brain by its adapting power makes the essential conditions of life much more nearly uniform than would at first be supposed from his varied habitat, the total expenditure in procuring heat, food, safety, and in reproduction together being about the same in most races and classes. Hence we do not look for much difference of longevity, even in different climes and different civilizations. It is when we come to extremes, however, such as do exist, in which men are living and not adequately contending with nature by their intelligence, but are getting worsted in the struggle, that we may expect appreciable variation in longevity; the expenditure is increased in one direction without being diminished in another, and consequently the longevity suffers.1 Thus, whilst the savages of Polynesia and of many parts of Africa,

1 The inhabitants of Iceland are stated to rarely attain old age, comparatively few reaching the age of sixty, but I have not found any statistical proof of this assertion. ('Aitken's Medicine,' vol. ii.) In the same work the terrible condition of the inhabitants of the Pontine Marshes is described from various sources, and it is clearly shewn that men living in such malarious conditions have life greatly curtailed, becoming old and exhausted before other men have reached their prime. These cases appear to be abnormal in their conditions of life, and no evidence is forthcoming as to whether hereditary diminution of longevity is brought about by the subjection of a population to such circumstances. Probably it is.

together with the semi-civilized Mongolidæ, and the highly-civilized Iapetidæ, are, through the action of their brain power, equalised as to potential longevity by equality in respect of accessibility of food and warmth, what the barbarous gain by the diminished expenditure implied in warmth, abundance, and absence of intellectual exertion, being made up to the civilized by the higher evolution both personal and social; yet there are extremes of misery and want, of cold and of heat, to which the most degraded savages are subject, not being sufficiently intelligent to cope with these difficulties, and to which classes of men even in the most civilized communities are born and bred, not allowed by the more fortunate to receive either necessaries or education, which no doubt entail upon these savages and these classes a much diminished potential longevity.

There is then perhaps reason to admit hereditary diminution of longevity in such cases as compared with the mass, though the hereditary character will probably cease to affect the second or third generation after removal from the injurious conditions specified. The same character of temporary heredity appears in families which for some few generations are often remarkable for longevity; or, on the other hand, through disease,1 intemperance, or other feeble

1 Disease may be regarded as increasing expenditure—entailing abnormal and useless expenditure, often in excess, by causing exhaustion, misdirected nutrition, &c.

ness in parentage, are equally remarkable for short life. It is in this regard (influence of disease) that the question of the average longevity or mortality of groups of men to their potential longevity deserves to be closely studied. At present, there are no data to solve the question as to the extent or nature of the influence of the one over the other, and an examination of the various life-tables given below shews that the relation is most inconstant (see p. 109 et seq.).

We may almost look upon excessively injurious conditions of existence and their effect on individuals as a definite thing comparable to a disease, being just as abnormal as in contrast with the most healthy state known to us; and we may say that no man with the disease 'Fuegian,' or 'Esquimaux,' or 'Australian,'1 would have as fair a chance of long life, however favourable his circumstances, with that exception, as the man who does not labour under the disadvantage of a long ancestry of degraded savagery, and is therefore free from such disease; just as we have no hesitation in saying that a man with hereditary phthisis, scrofulous, or cancerous tendency, has not so fair a chance of long life as the healthy man. And just as in the course of a few generations the offspring of the latter may become quite healthy, so may the offspring of the former, in so far as his hereditary tendency to short life is concerned.2

1 Or we may add, English mechanic,' or 'poverty and dirt.'

2 Mr. Hendriks, of the Universal Life Office, informed the writer that

H

With these preliminary remarks on the nature of the possible variations in human potential longevity, we may proceed to some facts, and their interpretation, by means of the relations shewn to exist in all organisms for longevity.

15. Sources of Information as to Human Longevity.

Before making enquiry, one is apt to suppose that a good deal must be known as to the probable duration of human life; that there are, at any rate, statistics of some nations or periods of which assurance companies make use. But there are statistics and statistics,1 and very few of the calculations relating to this matter are of real value. Besides statistics, as observed in a previous paragraph, we have general impressions either brought home by travellers or current amongst a people, and appearing in their sayings, poetry, traditions, and philosophy.

he believed himself that there is hereditary difference of life-tenure in various races. But he gave no facts, and probably the explanation here given of the apparent hereditary character may include all that he would contend for.

1 Professor Huxley most truly observes that there are many cases in which the admitted accuracy of mathematical processes is allowed to throw a wholly inadmissible appearance of authority over the results obtained by them. Mathematics may be compared to a mill of exquisite workmanship, which grinds you stuff of any degree of fineness; but, nevertheless, what you get out depends on what you put in; and as the grandest mill in the world will not extract wheat-flour from peascods, so pages of formula will not get a definite result out of loose data.'Anniversary Address to the Geological Society, 1869.