Letter from John P O'Brien, Associate Professor of Zoology, to Otto Loewi, New York University College of Medicine Thanks Loewi for the reprint of his essay, 'Reflections on the Study of Physiology.' Requests clarification of Loewi's statement suggesting that we may never understand 'the basis of the tendency toward and capacity for self-preservation' - offers two interpretations of these words and asks which Loewi means. 9 February 1955