It was with a deep sense of responsibility and of gratitude alike that I accepted the invitation to address you as your fourteenth Maudsley Lecturer; a sense of responsibility through the thought that, in a way, I come as a representative of American psychiatry; a sense of sincere gratitude for an opportunity to acknowledge a real personal indebtedness to British science and British medicine and British psychiatry, partly for what I received myself in the long years since my early post-graduate work in this country forty-three years ago, and partly for the influence British thought and work and practice has had upon certain developments, for which it is a pleasure to express our indebtedness and appreciation. Some of these relations and connections are little realized and little appreciated, and yet very illuminating and by no means only personal.

The thyroid gland has a profound influence on the mind, both in its emotional and its intellectual aspects. The emotional features of hyperthyroidism are too well recognized to need stressing. So, too, is the association between gross diminution of thyroid function and the mental incapacity of cretinism. It was suspected, therefore, that even in those types of mental deficiency in which diminution of thyroid function was not recognizable clinically, it might be possible to detect some evidence of abnormality in the thyroid gland by histological study. Further justification for presupposing the possibility of thyroid derangement may be found in the fact that in many conditions an association between the thyroid and thymus has been established, and that in mental deficiency the thymus undergoes premature atrophy.

Although the blood-urea level is not uniformly distinctive of any type of psychosis or phase of a psychosis, yet its estimation in general psychiatric practice is probably as useful as any other test or reaction in use to-day.