nce of acquired characters. To use the word "heredity" in such a
case is unjustified. Uterine infection has no bearing whatever on the
question.

Taking an historical view, it seems fairly evident that if diseases were
really inherited, the race would have been extinct long ago. Of course
there are constitutional defects or abnormalities that are in the
germ-plasm and are heritable: such is the peculiar inability of the
blood to coagulate, which marks "bleeders" (sufferers from hemophilia, a
highly hereditary disease). And in many cases it is difficult to
distinguish between a real germinal condition of this sort, and an
acquired disease.

The inheritance of an acquired disease is not only inconceivable, in the
light of what is known about the germ-plasm, but there is no evidence to
support it. While there is most decidedly such a thing as the
inheritance of a tendency to or lack of resistance to a disease, it is
not the result of incidence of the disease on the parent. It is possible
to inherit a tendency to headaches or to chronic alcoholism; and it is
possible to inherit a lack of resistance to common diseases such as
malaria, small-pox or measles; but actually to inherit a zymotic disease
as an inherent genetic trait, is impossible,--is, in fact, a
contradiction of terms.

(3) When we come to the effects of use and disuse, we reach a much
debated ground, and one complicated by the injection of a great deal of
biological theorizing, as well as the presence of the usual large amount
of faulty observation and inference.

It will be admitted by every one that a part of the body which is much
used tends to increase in size, or strength, and similarly that a part
which is not used tends to atrophy. It is further found that such
changes are progressive in the race, in many cases. Man's brain has
steadily increased in size, as he used it more and more; on the other
hand, his canine teeth have grown smaller. Can this be regarded as the
inheritance of a long continued process of use and disuse? Such a view
is often taken, but the Lamarckian doctrine seems to us just as mystical
here as anywhere else, and no more necessary. Progressive changes can be
satisfactorily accounted for by natural selection; retrogressive changes
are susceptible of explanation along similar lines. When an organ is no
longer necessary, as the hind legs of a whale, for instance, natural
selection no longer keeps it at the point of perfection. Variat