f a hobby, to
ascertain by experiments whether the effects of use and disuse are
inheritable.

Thus, then, there are amply sufficient reasons why there is a great deal
of direct evidence in the one case and but little in the other: such
little being that which comes out incidentally. Let us look at what
there is of it.

* * * * *

Considerable weight attaches to a fact which Brown-Sequard discovered,
quite by accident, in the course of his researches. He found that
certain artificially-produced lesions of the nervous system, so small
even as a section of the sciatic nerve, left, after healing, an
increasing excitability which ended in liability to epilepsy; and there
afterwards came out the unlooked-for result that the offspring of
guinea-pigs which had thus acquired an epileptic habit such that a pinch
on the neck would produce a fit, inherited an epileptic habit of like
kind. It has, indeed, been since alleged that guinea pigs tend to
epilepsy, and that phenomena of the kind described, occur where there
have been no antecedents like those in Brown-Sequard's case. But
considering the improbability that the phenomena observed by him
happened to be nothing more than phenomena which occasionally arise
naturally, we may, until there is good proof to the contrary, assign
some value to his results.

Evidence not of this directly experimental kind, but nevertheless of
considerable weight, is furnished by other nervous disorders. There is
proof enough that insanity admits of being induced by circumstances
which, in one or other way, derange the nervous functions--excesses of
this or that kind; and no one questions the accepted belief that
insanity is inheritable. Is it alleged that the insanity which is
inheritable is that which spontaneously arises, and that the insanity
which follows some chronic perversion of functions is not inheritable?
This does not seem a very reasonable allegation; and until some warrant
for it is forthcoming, we may fairly assume that there is here a further
support for belief in the transmission of functionally-produced changes.

Moreover, I find among physicians the belief that nervous disorders of a
less severe kind are inheritable. Men who have prostrated their nervous
systems by prolonged overwork or in some other way, have children more
or less prone to nervousness. It matters not what may be the form of
inheritance--whether it be of a brain in some way imper