must not blind us to the real analogy between heat and menstruation,
an analogy or even identity which may be said to be accepted now by most
careful investigators.[106]

If it is, perhaps, somewhat excessive to declare, with Johnstone, that
"woman is the only animal in which rut is omnipresent," we must admit that
the two groups of phenomena merge into or replace each other, that their
object is identical, that they involve similar psychic conditions. Here,
also, we see a striking example of the way in which women preserve a
primitive phenomenon which earlier in the zooelogical series was common to
both sexes, but which man has now lost. Heat and menstruation, with
whatever difference of detail, are practically the same phenomenon. We
cannot understand menstruation unless we bear this in mind.

On the psychic side the chief normal and primitive characteristic of the
menstrual state is the more predominant presence of the sexual impulse.
There are other mental and emotional signs of irritability and instability
which tend to slightly impair complete mental integrity, and to render, in
some unbalanced individuals explosions of anger or depression, in rarer
cases crime, more common;[107] but the heightening of the sexual impulse,
languor, shyness, and caprice are the more human manifestations of an
emotional state which in some of the lower female animals during heat may
produce a state of fury.

The actual period of the menstrual flow, at all events the first two or
three days, does not, among European women, usually appear to show any
heightening of sexual emotion.[108] This heightening occurs usually a few
days before, and especially during, the latter part of the flow, and
immediately after it ceases.[109] I have, however, convinced myself by
inquiry that this absence of sexual feeling during the height of the flow
is, in large part, apparent only. No doubt, the onset of the flow, often
producing a general depression of vitality, may tend directly to depress
the emotions, which are heightened by the general emotional state and
local congestion of the days immediately preceding; but among some women,
at all events, who are normal and in good health, I find that the period
of menstruation itself is covered by the period of the climax of sexual
feeling. Thus, a married lady writes: "My feelings are always very strong,
not only just before and after, but during the period; very unfortunately,
as, of course, they cannot