The proposal to have this meeting arose from biochemical studies. But we believe that the results obtained have wider implications in the field of physiology and cytology. Biochemists have taken a part in the study of events occurring at the synapse ever since the transmitter theory was first enunciated. In fact, one of the first successes of the new theory was a biochemical one: the interpretation of the action of physostigmine as an inhibition of an enzyme, now called acetylcholinesterase (Loewi & Navratil 1926). However, until recently the role of the biochemist in the study of synaptic transmission has been an ancillary one. He has provided information on the enzymic equipment of neurons, especially the equipment with enzymes involved in transmitter formation, and he has also studied transmitter inactivation. But now, in the past year or two, the biochemists have also begun to share in the study of the events that occur during transmission. These recent observations were made on adrenergic neurons. To the student of adrenergic systems the transmitter theory has been particularly relevant. The catecholamines have a dual function. In the chromaffin tissue they are secreted as true hormones, and at the endings of adrenergic neurons they are released as transmitters. It was this link that Dr Arnold Welch and I had in mind when we wrote the paper in which we described our early observations on chromaffin granules. We ended the discussion of this paper, dedicated to Otto Loewi on the occasion of his eightieth birthday, with the sentence: ‘Such an interpretation would be in harmony with a concept that regards “ secretion” from glandular tissue and “ liberation” from nerves as events that are fundamentally related’ (Blaschko & Welch 1953).