[Footnote A: I am indebted to Professor McDougall's book for
information here given.]


These experiments all shew the trend of intelligence (and with it will
power or power of concentration, and what we may call general
capacity) to be more concentrated in the so-called higher grades of
society, and to be less and less evident as we descend in the scale
from skilled to unskilled workers. It would, of course, be clear to
all that the children of mentally deficient parents can only be a
burden on the State or can rarely contribute anything of value to the
common weal.

Now the teaching and advocacy of methods of conception control is most
easily assimilated and practised by the intelligent classes; indeed,
we may say with certainty that such methods can only be used
effectively by the intelligent members of the community, such as
leisured, professional and mercantile classes, skilled artisans and
better class workers, whereas the lowest type of casual labourers
whose home conditions render the use of preventive methods difficult
or impossible, and the mentally deficient and criminal classes, are
unaffected by such teaching.

The result in a few generations must be a marked decrease in the
numbers of the intellectual and efficient workers, while the
hopelessly unfit continue to produce their kind at the same rate as
before.

The figures given do not suggest that individuals with marked ability
are to be found in the upper classes only, but they do indicate that