It will be seen at once that this seems to preclude any possibility of a
child's inheriting from its parents anything which these did not
themselves inherit. The bodies of each generation are, so to speak, mere
"buds" from the continuous lines of germplasm. If we _develop_ our
muscles or our musical talent, this development is of the body and dies
with it, though the physical basis or capacity we ourselves inherited
is still in the germplasm and is therefore passed along to our
children. We may also furnish our children an environment which will
stimulate their desire and lend opportunity for similar or greater
advancement than our own. This is _social inheritance_, or the product
of _environment_--easy to confuse with that of _heredity_ and very
difficult to separate, especially in the case of mental traits.

It will likewise become clear as we proceed that there is no mechanism
or relationship known to biology which could account for what is
popularly termed "pre-natal influence." A developing embryo has its own
circulation, so insulated from that of the mother that only a few of the
most virulent and insidious disease germs can ever pass the barrier. The
general health of the mother is of utmost importance to the vitality,
chances of life, constitution and immunity from disease of the unborn
child. Especially must she be free from diseases which may be
communicated to the child either before or at the time of birth. This
applies particularly to gonorrhoea, one of the most widely prevalent as
well as most ancient of maladies, and syphilis, another disastrous and
very common plague which is directly communicable. As to "birthmarks"
and the like being directly caused by things the mother has seen or
thought about, such beliefs seem to be founded on a few remarkable pure
coincidences and a great deal of folk-lore.