the thyroid and adrenals are excellent examples.

It seems to be the fate, however, of all supporters of new theories to
run into extravagances. Darwin had to remind his enthusiastic disciples
that Natural Selection could not create variations, and we may feel some
confidence that Hering, were he alive, would urge his followers to bear
in mind that memory cannot create a state of affairs which never
existed. So far we may certainly say that these internal secretions do
produce certain physical effects, some of them effects not to be
suspected by the uninformed reader. There seems to be very good evidence
that the growth of antlers in deer depends upon an internal secretion
from the sex-gland and from the interstitial tissue of that gland; for
it is apparently upon the secretions of this portion of the gland that
the secondary sexual characters depend, and not merely these, but also
the normal sexual instincts. And this takes us a stage further. The
extreme claim is that all instincts, in fact all thoughts and
operations, are in the last analysis chemical or chemico-physical. Let
us examine this claim for a moment. The adrenals are two inconspicuous
ductless bodies situated immediately above the kidneys. Not many years
ago, when the present writer was a medical student, all that was known
about these organs was that when stricken with a certain disease, known
as Addison's disease from the name of its first describer, the
unfortunate possessor of the diseased glands became of a more or less
rich chocolate colour. To-day we know that the internal secretion of
these organs is a very powerful styptic, and there is good reason to
believe that a copious discharge accompanies an unusual exhibition of
rage. When we are told things of this kind we must first of all remember
that the adrenalin does not cause the rage, though it may produce its
concomitant phenomena. If a man flies into a violent passion because
someone has trodden upon his corns, and there is a copious flow of
adrenalin from the glands, it is not that flow which has caused his
rage. It may be the flow from the interstitial tissue of the sex-glands
which engenders sexual feelings, but then those are almost wholly
physical, and only in a very minor sense--if even if any true
sense--psychical. Persons who take the extreme view have never yet
suggested that there is a characteristic hormone connected with those
psychical attributes alluded to in the chapter of the Co