The role of the unconscious in the etiology of mental diseases is a dominant one, and the comparative indefiniteness of the de limitations of the various types of mental dis orders is due to the newness of any scientific knowledge concerning the unconscious portion of mental functioning. The neurologist should have, though unfortunately comparatively few do, as thorough a knowledge of the unconscious mental mechanisms as can be acquired, in addi tion to the medical specialist's knowledge of anatomy, physiology and histology. Recogni tion of the unconscious as a factor in the causes of mental disease requires the understanding that the present day unconscious is the direct descendant of the prehistoric consciousness. It is as if the human psyche were like the earth's surface constructed in strata, the lowest of which was the earliest deposited; much, too, as if the conscious life of successive genera tions from the earliest human and animal life were retained in the psyche of the present day as are the annual rings of growth in the stems of trees. The part played by the conscious or unconscious mental factor in the vegetative or visceral physiology is less evident to the general student than that played by them in the sensori motor systems or in the psychical or symbolic systems. Yet there are good reasons to sup pose that even so serious a disease as pulmo nary tuberculosis may be helped, if not cured, by the patient's being taught how to secure con trol of the unconscious portion of his ego. The exciting causes for this disease, as well as of hysterical coughing and asthmatic attacks, may lie either in the physicochemical, the sensori motor or the psychical level. The connection between the diseases of the glands of internal secretion, the thyroid, parathyroid, hypophysis, pineal gland, etc., and the manifest mental con dition is shown in the case of cretinism and of exophthalmic goitre. In these diseases it is quite as likely that the cause is mental as that it is physical, and in such event, we should have to regard exophthalmic goitre, as a symp tom of a mental disease rather than the mental factors accompanying it as symptoms of the physical disease. Similarly the very widespread disorder, migraine, is possibly to be regarded as the projection upon a vegetative system, the vaso-motor, of a conflict which originates in the psychical level. Conflicts at the psychical level, which are usually caused by the lack of adap tation to social environment referred to above, may be projected upon the sensori-motor sys tems and produce retinitis, progressive facial hemiatrophy, various facial palsies, vertigoes, auditory and visual aphasia, tic douloureux, sciatica, shingles and peripheral palsies, and other diseases, many of which were considered up to recent times to have only physical causes.* But the conflict, conscious or unconscious, which occurs at the psychical or symbolic level of the ego is manifested in predominantly men tal modes in the so-called neuroses, psycho neuroses and psychoses. Of the psychoneuroses the commonest are hysteria, compulsion neuro sis and anxiety hysteria. Of the actual neuro ses there are anxiety neurosis and neurasthenia, while special cases present mixtures of these neuroses. As a mental disease, and not as popularly used to denote an uncontrolled emo tional state, hysteria is now regarded as a par tial dissociation of the personality, in which certain mental elements, namely, emotions and ideas, have been rejected from consciousness into the unconscious where they have an exist ence which is at least partly independent —an existence which is of vital importance to the welfare of the individual because it is an ex istence in which the split-off ideas and emo tions have a growth or development of their own. This development is different in hysteria and in compulsion neurosis. In hysteria the mental elements, which are repressed from con sciousness into the unconscious, direct or con trol a portion of the libido in such a way that its force has an incidence not upon the world of external reality, as is the case with the average person, but in the shape of work done in some shape or other. On the contrary the incidence of' the libido falls upon the physi ological functions themselves or upon certain of them through a variety of symbolic selec tion. This process, which is known as hys terical conversion, produces very many so called symptoms, mostly of a bodily nature. There results from this a large number of dis orders which the general practitioner is prone to regard as having only a physical cause, and he prescribes drugs, which rarely have the de sired effect. Possibly the commonest form of this is the hysterical headache, which is rarely recognized of psychogenic origin, although it is so completely analogous to the "nine o'clock illness" of school children who use this gentle form of unconscious malingering as a means for escaping their responsibilities. "An adult ought to make a call upon a recently bereaved friend." This is recognized as a distinct obli gation but the patient's infantile necessity of escaping reality and seeking pleasure makes the duty seem a very onerous affair. Thus arises a conflict between duty, born of conscious ap preciation of the social obligation, and desire, born of the childish inability to make the neces sary sacrifice of personal comfort. As a result the patient develops a headache and so, being ill, does not have to go. While the mechanism in other hysteric conversions is more compli cated, it is no less clearly proved, so that the number of what are ordinarily taken as symp toms having a merely somatic cause, and which are through analysis seen to be merely hysteri cal conversions, is augmented daily. Disturb ances of sensibility, such as hemianwsthesia or insensibility to touch and pain on one side of the body only, disturbances of motility such as choreiform movements, tics and certain occupa tion spasms, disturbances of speech, sometimes including stuttering, visceral disturbances show ing vomiting and diarrhoea, vaso-motor disturb ances and emotional disturbances, particularly in cases of great exaltation or depression, are all likely to be caused by the hysterical dissocia tion before mentioned, in which some mental factor is repressed and therefore driven with out the pale of conscious control.
In compulsion neurosis there is no conver sion, which implies a shifting of the incidence of the libido power from the external world, which is its natural goal, to the physiological processes of the individual; but there is an other kind of shift, namely, from the external world to the mental states themselves. In this condition the numerous physical symptoms mentioned as being found in hysteria are gen erally absent, but their place is taken by varia tion from the conventional modes of thinking. Such variations to be sure are far from un pleasant, if they do not become too great, for they add much of piquancy and interest to a person's character. But when the departure from the conventional is excessive and both compulsive and unaccountable, the condition merits the term neurosis and requires treatment from the analyst. There are compulsive thoughts, compulsive doubts, fears, acts, rituals of dressing and undressing or eating for which this kind of neurotic can give no reason. He generally does not attempt to rationalize them but admits he does not know why he always has to act or think in his own peculiar way. Analysis has convinced Freud that "obsessions are always transformed reproaches, returning from repression, which always refer to a pleasurably accomplished sexual action of child hood" and that "the compulsive ways of think ing and acting are only substitutes for the reproaches which are symbolical distortions formed in order to prevent a recognition on the part of the patient of the real meaning, so as to keep from his consciousness a realiza tion of the circumstances of his guilty conduct." Paranoia is a group of mental diseases con taining the paranoia as defined by Kraepelin, and various mixed aberrant forms, some of which are called paraphrenias. In general it is a disease in which there are delusions of perse cution that have been pretty well systematized. The disease progresses usually through four rather well-defined stages. In the first the patient is unduly concerned about his health, and particularly about what goes on around him in relation to himself. That is, he con siders more things are said and done with reference to himself than does the ordinary person, and he begins to reason it all out that there must be some agreement in the actions of persons or things around him, usually for his discomfiture or ruin. Hallucinations of hearing are common. The result of his think ing himself to be the victim of persecution is that he sometimes becomes very dangerous, and attacks the persons whom he regards as his persecutors. In advanced cases the system ideas deas worked out in justification of the sus picions of persecution or conspiracy is very elaborate, and includes frequently falsifications of early memories, which contribute the grain of truth in some of the projected reproaches. Another classification of the paranoia group of mental diseases is that into two divisions, the original and the acquired, the first being the inevitable development of a character which was of such a constitution as to develop into exactly this form of mental disease, in spite of an environment even partly favorable to a wholesome life, and the second, the effect of an untoward environment upon a neural con stitution which might in more favorable cir cumstances have escaped this fate. According as hallucinations are or are not present, these groups are further divided respectively into paranoia hallucinatoria and paranoia combina toria. Furthermore the individual cases are described as persecutory, expansive, querulous, litigious, inventive, reformatory, religious and erotic, according to the forms which the more prominent mental symptoms show. A third division of the paranoia group is into delirium of interpretation and delirium of revindication. In the first the erratic element is in the in terpretation of the factors of the environment of the patient, who remains otherwise quite clear minded, and in the second there is a tendency toward the formation of a fixed idea, either egocentric or altruistic. As paranoia was considered an incurable, progressive and chronic disease, 'those cases which through analysis have been shown to have at the basis of them an idea that could be traced out and corrected, and which therefore have been called acute paranoias, necessitated a further recon struction of the concepts underlying the classi fication. The result of this is that the content of the mental states in this form of disease is not now considered so indicative as the mental mechanisms involved. This implies again that it is not so much the delusion, or the suspicion itself, or any other of the symptoms, which used to be considered characteristic of the dis ease, but it is the inability on the part of the patient to adapt his ego to those ideas which form the so-called content of the paranoid state. The delusion, for example, is found to have been made by the patient for the pur pose of making a certain emotion tolerable which he could not get rid of. The removal of the delusion would not in such a case help, for another would have to be supplied in its place, to explain the original emotion, which would itself remain. The emotion or a lack of control over the emotions is thus seen to be the most fundamental cause of the disease. The explanation of paranoia consists, there fore, in the emotional lack of control, which fixes upon certain ideas and is unable to chug them, and furthermore in an exaggeration 3i the mechanism of projection. (See Mecisis ISMS, MENTAL). Finally Sigmund Freud state that paranoia is dependent upon a homosesnu fixation in the psychosexual development of the individual. Treatment of paranoia has ben more earnest and determined of late, as moo and more cases have been handled with grease success, but it is to be remembered that the curable cases are now by many regarded k. only paranoid forms of other mental disease% and that the true paranoiac is known as par anoiac virtually only by the failure of all effon to improve him. Psychoanalysis is the osly means by which any satisfactory knowledge can be gained of the unconscious mechanisms dominating any given case, and only by a thorough study can it positively be determined how much or how little can be acoomplishee in the way of therapeusis.