B YTHE institution of this lectureship in diseases of children it was the intention of The Canadian Medical Association to pay tribute to Dr. A.D. Blackader, a great pioneer in pediatrics in this part of the world, a distinguished author and editor, and a man devoted to the highest ideals in medicine. I am greatly moved by the honour conferred on me, my department and my University by The Canadian Medical Association in inviting me to deliver this lecture. I belong to those people who will never forget all that Canadians did for the liberation of The Netherlands and the friendship that Canadian doctors showed to many of my colleagues and to me after the liberation. Without entering into too many details, I wish to discuss a disease of which I gave the first clinical description in 1928, namely glycogen disease, also called glycogen storage disease or glycogenosis. I have been able to follow the clinical course in the first two cases of this disease, described by us, during all of the intervening years. Moreover, together with my co-workers, I have in recent years studied certain aspects of the disease that of late have, both from the clinical and the biochemical points of view, been of interest to many clinicians and research workers. The name glycogen disease is used to indicate a congenital and sometimes familial error of carbohydrate metabolism leading to an abnormal accumulation of glycogen in certain organs. This glycogen cannot be mobilized or can be mobilized only with difficulty. The accumulation of glycogen usually gives rise to great enlargement of one or more organs. The accumulation is mostly due to a disturbance of a varying nature in the function of the normal intracellular enzyme system of carbohydrate metabolism. Until 1952 only two types of glycogen disease could be distinguished, namely the type in which the accumulation of glycogen in, and hypertrophy Delivered at th.