200 The American Naturalist. [March, 
early years and even far into the period of maturity the phy- 
siological activities prevail. Childhood and early youth are 
characterized by the aimlessmovements of spontaneity and 
the prodigal expenditure of physical force ; later on the psycho- 
logical life rises in importance and attains its maximum 
when the physiological life is on the wane. This continues 
until the decay of old age sets in. 
A grander series of changes remains yet to be considered. 
This is suggested by the query, how does the quantity of 
human life existing on the globe at the present time compare 
with the quantity of the antecedent times? Whoever reviews 
the history of the race during the nineteenth century as related — 
to its history in previous times will observe a tremendous — 
acceleration in the rate of living, and a vast augmentation in 
the intensity of human life. Notable among the causes which 
have secondarily conspired to this end, may be mentioned the — 
centralization of populations. Within a century, according to — 
the London Journal of Statistics the relative populations of the 
country and city of England have changed sides. Up to 
about 1840 the rural population exceeded the urban. About — 
that year they were equal, and ever since, the cities have had — 
a constantly increasing majority. The same is true in general — 
of other civilized countries. Facts like these tend to show — 
that the society of modern life is becoming more consolidated, 
and hence the aggregate of human experiences is becoming 
increasingly intense from year to year. Among the primary — 
causes which have brought about this consolidation, are the i 
improved facilities of travel, commerce, and communication 
between mind and mind. Not only have they done this, 
they are the indispensible conditions of an intricate co-opera- 
tive existence. But these are only a few of the many 
which enter the problem of this augmentation of life. 48 
differentiation of pursuits and the widely diversified pr? 
