coming a cause of haemorrhage; or, in other
words, stimulation of the brain cannot be likened in its effect to
galvanic stimulation of a spinal nerve. But if stimulation of the brain
does not paralyze, it must increase the tonicity of the vaso-motor
centre, and hence the force and regularity of the circulation. Up to a
certain point, these characters do indeed increase, with increase of
pressure in the cerebral blood-vessels. They increase also during
intellectual operations, unattended by emotion, in which a similar
increase of pressure must take place, on account of the afflux of blood
to the cerebral hemispheres, when these are aroused to activity.

These facts already indicate a radical difference between the nature of
the cerebral actions involved in emotion and in thought. From them also
we should infer in all cases where vaso-motor paralysis was apparently
traceable to excess of cerebral activity, either _that exhaustion had
already occurred, or that the activity was not intellectual but
emotional_. In the first case, we should be immediately brought to our
fourth possible condition for uterine haemorrhage, dependent on
modifications of the cerebro-spinal system. It is admitted, as the
result of many experiments and pathological observations that need not
here be quoted, that exhaustion of certain parts of the brain and spinal
cord may induce vaso-motor paralysis, and that, if a cause for
haemorrhage is already in operation, a passive flow of blood may be
indefinitely increased. Such a course is the menstrual crisis, without
which even the vaso-motor paralysis is usually unable to determine
uterine haemorrhage.[40] In connection with it, physical exercise, pushed
to the point of exhausting the spinal cord, and the peculiar centre in
its lumbar portion, or mental effort so excessive and prolonged as to
exhaust the brain, and the general vaso-motor centre, might become
causes of menorrhagia.

It is evident, however, that if such exhaustion had been produced
previous to the menstrual epoch, the effect would be precisely the same
as if the morbific causes operated only at the time of menstruation.
From this point of view the precaution suggested by Dr. Clarke, of
intermitting intellectual effort during the menstrual period, would be
inadequate whenever it was not superfluous. But in Dr. Clarke's theory
this period has a peculiar influence in rendering morbific conditions
that at other times are innocuous. This, in v