SUCH populous nations as India, China, Japan, and certain
European countries have long engaged the interest of lay
thinkers, and excited alarmists who fear the downfall of
"Nordic superiority" through the inevitable diffusion of
"hordes of olive-skinned Asiatics" and other "undesirables."
During and following the World War an ever-increasing num-
ber of primary and secondary contacts were made, and as a
result, nations, more than ever before, have become so insep-
arably linked that what affects one ultimately affects others.
Not only international but also national complications have
arisen. Since the World War such organizations as the Ku
Klux Klan and the restriction of immigration are indicative
of some of the problems within our own borders. Conse-
quently problems of population resulting from racial diffu-
sion have increased as a greater breadth of culture contacts
have been made, and as certain opinions concerning these
have become more and more biased.

On the other hand, scientists and careful students have
sensed pertinent problems inherent in the population situa-
tion, and are seriously studying the various forces that are
serving as controls upon the quantity and quality aspects of
population. Among these might be mentioned the unparal-
leled increase in numbers, the rapid depletion of our mineral
resources, the pushing of our food supply towards its optimum
limit, the decline in the birth rate of the "upper" classes,
the gravitation towards the cities, the effects of a curtailed
immigration and the mixture of races. These and kindred
phases of population have been dealt with from many angles
and with varying amounts of prejudice and scientific exacti-

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