When you did me the very great honour of calling on me to deliver the Maudsley Lecture, I was told that it had been decided that these lectures should be devoted alternately to scientific psychiatry and to subjects of general popular interest, and that the subject of my lecture was to be scientific. I decided that with a year's notice the active preparation of the lecture might well be postponed for eleven months, and that during this gestation period I might hope to fix on one of the many aspects of pathological or physiological science of sufficient interest to justify a not too technical exposition to a mainly clinical audience.

The hereditary aspect of mental disease is at the present time a preferential topic of research, and the importance of constitutional factors in the causation of neuroses and psychoses is generally admitted. In many instances the term “constitution” is merely a hypothetical “X” introduced because of the absence of other facts which could account for clinical symptoms. Constitution is given a positive meaning only if it is identified with hereditary equipment, which has to be assessed by the careful analysis of the clinical aspect of the disease as a whole, including its hereditary and familial aspects, as well as environmental and other exogenous causal factors. Unfortunately, psychiatric illnesses as a whole do not lend themselves readily to this type of investigation. It is usual, therefore, to apply the results of studies of heredity in non-psychiatric conditions to psychiatric illnesses themselves. As neurological conditions are the most closely allied to psychiatric ones, they are most commonly used. One of the most convenient types of illness to study from this point of view is Huntington's chorea, not only because of its psychiatric aspects, but also because of its striking symptomatology and course.

Originally the conception of disturbances of the cerebral circulation was closely associated with that of gross arterial and venous disease, and it was in these conditions that the typical pictures of hæmorrhages, hæmorrhagic and anæmic infarctions (softenings), scars and cysts as their sequelæ were first studied. These sequelæ are in all essentials the same in the brain as in other organs with similar vascular arrangements, such as the kidney and the spleen, with the exception of some peculiarities due to special structure or special staining reactions. Recent ischæmic necrosis of the grey matter appears in Nissl-stained specimens as areas of pallor, and examination under high magnification often reveals a special type of ganglion-cell change called ischæmic by Spielmeyer (16), which so far has maintained its reputation as being highly specific. A further peculiarity is provided by the activity of the glia in all processes of breakdown and repair. In vascular disease especially, a type of mobile glial-mesodermal activity is met with (Spielmeyer (16)), that is to say, the glia acts jointly with the mesenchymal tissue in the production of scavenger-cells and of fibres.

The immature psyche of the child is at least as easily upset by both organic and psychological factors as is that of the adult. The slightest fever or digestive upset may, in a child, lead to bad temper, lack of appetite and sleeplessness. In spite, however, of the ease with which minor psychological disorders are brought about, the severe mental disturbances constituting the psychoses are very infrequently met with. Those to be described occur in the early years of life. Some of them resemble serious behaviour and personality disorders; some would seem to be of organic ætiology. Common to all are regressive changes leading especially to loss of recent attainments, and to some disorganization of the personality following a hitherto normal development.

The term “dysentery” in mental hospitals may be regarded as applicable to a clinical entity characterized by symptoms of abdominal pain, rise of temperature and passage of blood and mucus. The causative organisms are various, but that occurring most frequently and persistently is the Bacillus dysenteriæ of Flexner. This paper deals exclusively with this type of asylum dysentery.