as is seen, in an exaggerated way, in persons who have
so-called Dual Personality. These patients suddenly fall into a
secondary state, in which they forget all the events of their ordinary
lives, but remember all the events of the earlier periods of the
secondary personality. This state may be described as "general"
amnesia, in contrast to the "partial" amnesia of the other cases
given, in which only particular classes of memories are impaired.

The impairment of memory with advancing years also illustrates both
"general" and "partial" Amnesia. The old man loses his memory of
names, then of other words, then of events, and so gradually becomes
incapable of much retention of any sort.

_Defects of Will--Aboulia._--A few words may suffice to characterize
the great class of mental defects which arise on the side of action.
All inability to perform intentional acts is called Aboulia, or lack
of Will. Certain defects of speech mentioned above illustrate this:
cases in which the patient knows what he wishes to say and yet can not
say it. This is the type of all the "partial" Aboulias. There may be
no lack in determination and effort, yet the action may be impossible.
But, in contrast with this, there is a more grave defect called
"general" Aboulia. Here we find a weakening of resolution, of
determination, associated with some lack of self-control showing
itself frequently by a certain hesitation or indecision. The patient
says: "I can not make up my mind," "I can not decide." In exaggerated
cases it becomes a form of mania called "insanity of doubt." The
patient stands before a door for an hour hesitating as to whether he
can open it or not, or carries to its extreme the experience we all
sometimes have of finding it necessary to return again and again to
make sure that we have locked the door or shut the draught of the
furnace.

With these illustrations our notice of mental defects may terminate.
The more complex troubles, the various insanities, manias, phobias,
etc., can not be briefly described. Moreover, they are still wrapped
in the profoundest obscurity. To the psychologist, however, there are
certain guiding principles through the maze of facts, and I may state
them in conclusion.

First, all mental troubles involve diseases of the brain and can be
cured only as the brain is cured. It does not follow, of course, that
in certain cases treatment by mental agencies, such as suggestion,
arousing of expectation, fait