Silent Spring by Rachel Carson

mental defects often accompany the sterility caused by this condition. In c ontras t, an individual
who receives only one s ex chromos ome (becoming XO ins tead of either XX or XY) is actually
female but lacks many of the secondary sexual characteristics. The condition is accompanied by
various physical (and sometimes mental) defects, for of course the X chromosome carries genes
for a variety of cha racteris tics. This is known as Turner’s s yndrome. Both c onditi ons had been
des cribed in medical literature long before the caus e was known.
An immens e amount of work on the s ubject of chromos ome abnormalities is being done by
workers in many countries. A group at the Univers ity of Wis cons in, headed by Dr. Klaus Patau,
has been concentrating on a variety of congenital abnormalities, usually including mental
retardation, that s eem to res ult f rom the duplication of only part of a ch ro mos o me, a s i f
s omewhe re in the f ormation of one of the germ cells a chromos ome ha d broken and the pieces
had not been prope rly redis tributed. Suc h a mis hap is likely to interfere with the normal
development of the embryo. According to present knowledge, the occurrence of an entire extra
body chromos ome is us ually lethal, preventing s urvival of the embryo. Only three s uch
conditions are known to be viable; one of the m, of cours e, is mongolis m. The presence of an
extra attached fragment, on the othe r hand, although s erious ly damaging is not necess arily
fatal, and according to the Wisconsin investigators this situation may well account for a
s ubs tantial part of the s o far unex plained cas es in which a child is born with multiple defects ,
usually including mental retardation. This is so new a field of study that as yet scientists have
been more concerne d with identifying the chromos ome abnormalities associated with disease
and defective developme nt than with s peculating about the caus es. It would be foolis h to
ass ume that any s ingle agent is res pons ible for damaging the chromos omes or caus ing their
erratic behavior during cell division. But can we afford to ignore the fact that we are now filling
the environment with chemicals that have the powe r to s trike directly at the chromos omes ,
affecting them in the precis e ways that could caus e s uch conditions? Is this not too high a price
to pay for a sproutless potato or a mosquitoless patio? We can, if we wish, reduce this threat to
our genetic heritage, a poss es sion that has come down to us through s ome two billion years of
evolution and selection of living protoplasm, a possession that is ours for the moment only,
until we mus t pas s it on to gene rations to come. We are doing little now to preserve its
integrity. Although chemical manufacturers are required by law to test their materials for
toxicity, they are not requi red to make the tes ts that would reliably demons trate genetic effect,
and they do not do s o.