The subject of my address is one of immense importance to the community, and of particular concern to a very large number of individuals.

At the outset it is necessary to point out that although this Report is the result of deliberations extending over a period of four years, it does not profess to deal in an exhaustive manner with every aspect of mental deficiency. The main purpose of the Committee was to consider the problem from the administrative point of view and, whilst many other matters have been dealt with, the subject of mental deficiency is so large that these have necessarily only received somewhat brief mention. At the same time the Report extends over a considerable field, and there is little doubt that it will be regarded as an important contribution to the subject and one deserving of the careful attention of all who are in any way concerned with this class of persons. It is obviously impossible for me to discuss, or even refer to, all the matters which have been dealt with in the four parts of this Report; I shall accordingly confine my remarks to the more salient features.

Although my object is to initiate a discussion on this subject free from the trammels of the past, I must, I fear, for a brief time deal with it historically.

In recent years research into mental disorders has tended to become more and more the study of the pathology of the living. The advance of biochemistry has contributed in great measure to this practice. Although bacteriological research has, in recent years, been more extensively undertaken in connection with focal infection, it has, in the opinion of most, yielded disappointing results. The study of focal infection by bacteriological methods alone will not, I am afraid, lead us very far. Endeavour should be made to correlate its local and remote effects in disordered hæmopoiesis, disordered metabolism and disordered endocrines in relation to the internal economy of the patient. In mental disease especially this implies a knowledge of the individual's potentialities that have been predestined by heredity, and later moulded by environment—factors which largely determine the psychopathic tendencies of every one of us. The bacteriological researches of Ford-Robertson and McRae (1) strongly suggest that in mental disorders we are confronted by bacteria of a special type, which as chronic infective agents can probably only adapt themselves to a certain group of the general community having a neurotoxic susceptibility. If, then, we are to make further progress in this direction, we must search for and apply new methods of bacteriological technique, study our results, and attempt to correlate cause and effect. In this relation I shall refer to special methods which are an elaboration of my father's work, the value of which time and experience may prove. In spite of the great importance of the biochemical researches of recent years, I think it will be agreed that some of us, especially those who are clinicians, feel disappointed that so far they have not given us as much indication for scientifically applied treatment as we had hoped. May I suggest that the explanation for this is two-fold. Firstly, in forming the basis of any research the present tendency is to take mental disorders in groups, for example, dementia præcox, which has a wide range of symptoms and between which and other groups it is difficult to draw a line of demarcation. It seems to me that our knowledge of the somatic factors underlying mental disorder is as yet so limited that attempts to continue on these lines will lead us only hesitatingly along the path of progress. Are we not still at the stage where our efforts should be concentrated more on the individual as a problem in pathology which, when solved as far as our knowledge permits, can be correlated in the future with his or her psychogenic group? The second point is that in many instances our scientific work tends to run in too narrow channels; thus it must be frequently lacking in the invaluable support of parallel knowledge in other branches of laboratory and clinical experience. The most obvious example is the lack of adequate collaboration between the biochemist and bacteriologist. I know of no two sciences that can be welded together so opportunely. This combination can be taken a stage further: active and intelligent co-operation with the clinician and X-rays and therapeutic specialists should be sought to enable us to appreciate better the intricate problems we have to face. Some of you may, with reasonable grounds, accuse me of theorizing, and I should at this stage like to mention that before I attempted to put these considerations into practice in cases of mental disorder, I had had the opportunity of carrying out exactly similar lines of research on some hundreds of non-mental patients in hospital and private practice. The majority of them were cases obscure in ætiology and symptomatology. This scientific survey proved to me at least the value of comprehensive work on the individual, and how it enabled one to diagnose and treat many cases with some hope of success. During my two years at Wantage House (the new acute hospital attached to St. Andrew's), I have attempted to carry out what this experience has taught me, with the added advantage that the patients have been under my personal care. Further, there has been every facility for dental and general X-ray diagnosis, and, lastly, ample scope for treatment. The success of such a scheme is only possible by organization and the team spirit, and in this I have been singularly fortunate. The cases I am bringing to your notice are 4 out of some 120 which have been subjected to comprehensive overhaul. I will try to emphasize the salient features in each and correlate them with the mental disorder presented. In this way you can judge for yourselves if we have learnt anything that may in the future lead to a clearer conception of what may underlie at least some forms of mental disorder.

Jean Martin Charcot, Physician to the Salpêtrière, and described by his biographer as the Prince of Neurologists, was an Honorary Member of this Association and lived from 1825 to 1893. Though the centenary of his birth, I believe, passed unnoticed in this country, he was in his day a master in clinical medicine and pathology, and his loss was keenly felt both at home and abroad.

The migration of chloride in the blood was first investigated by Hamburger (1) who showed that when blood is exposed to increased tensions of CO2 there is a shift of chlorine ions from the plasma into the corpuscles. This phenomenon is known as the Hamburger phenomenon or chloride shift.

Inasmuch as the following is a summary of results of investigations into the pathology of mental disorders that have been conducted at the Central Pathological Laboratory at the Maudsley Hospital during the past few years, I shall deal with the general results obtained by my co-workers in the broadest fashion, alluding only to such facts as appear to be relevant to the hypothesis I am putting before you. When the present investigations were begun we had already abundant evidence of anatomical lesions occurring in schizophrenia, worked out in this laboratory by Sir Frederick Mott (1), (2), (3), assisted by Mr. Geary. The completeness of this evidence is a matter of history and is not now seriously disputed. (A few of the slides from the collection left to the laboratory by Mott were here shown.)

Psycho-ANALYSTS and other psychiatrists agree, I take it, that there are multiple causes for every mental breakdown. The exciting cause may not always be discoverable, but would be sought, if wanted, in the period immediately preceding the onset. Contributory causes can occur throughout life, from birth to the date of onset. It is agreed, also, that in addition there must be a predisposition (though the strength of this as a causal factor varies, roughly, in inverse proportion to the others). It is in the localization of the predisposing (and specific) factors that authorities differ. The older psychiatrists confined it to the lifetime of the ancestors; psychoanalysts accept, in general, what they have been told about ancestral responsibility, but have focused attention, as regards predisposition for subsequent breakdown, on a later period, namely the first five or six post-conceptional years. This they regard as the developmental period of the psyche, and they consider that influences at this time modify the organization in process of formation in a way that cannot occur later, but is not entirely predetermined in the germ-plasm. The difference is not merely temporal but also qualitative, for while other causes are mainly general (with perhaps some exception as regards heredity), the infantile predispositions are specific. That is, they not only partly determine liability to a breakdown under stress, but play the chief part in determining the kind of breakdown to be expected should one occur, and also the basic layers on which various character formations are built, although the superstructures may be very varied.

In an earlier article (vide p. 107) a preliminary report was made on the treatment of epilepsy by peptone, B. coli and papaverine sulphate; in the intervening months extended opportunity has arisen for comparing the various methods of treatment and endeavouring to form some opinion of their efficacy.

The recent articles by Corper on a new method for the cultivation of the tubercle bacillus have stimulated interest in what has always been a difficult and tedious performance. Since cultural methods hitherto have not been much more delicate in the detection of tuberculosis than the microscopic examination of smear preparations of sputum and tissues, the latter has remained the popular choice, especially in ordinary hospitals. The guinea-pig inoculation method is unhandy and too expensive, and in any case detection of the bacilli in the inoculated animal has to be done by a microscopic smear preparation. The examination of smears of sputum and tissues seldom gives positive results in those cases where doubt exists. A negative result from a microscopic examination of a smear cannot be relied upon.

Physiologists, when experimenting with the frog, customarily make selection of one sex. This, being done to ensure constancy of experimental conditions, presumes the possible existence of a sexual modification of results—a presumption I find justified, for, having over many years simply selected the frog of largest size, which one day was male and another female, I can record the following variations of results according to sex.

In the present communication I propose to consider the nature of the excitation processes mediating the thoughts of people, met with in all walks of life, who are distinguished from others by their enthusiasm for certain things, or ideas. For example, the person in love is distinguished from others by his, or her, enthusiasm for a particular individual of the opposite sex. The process of developing that enthusiasm, or of falling in love, I take to be a perfectly natural process to which everyone is susceptible, but, love being blind, it becomes of interest to consider how that blindness is brought about.