Hoskins and Hoskins cannulated the gland in immobilized living fish, collected its secretion, and compared its volume with the amount of urine production but were unable to come to any conclusion as to its function. In the early 1960s, J. Wendell Burger published a series of studies on the function of the rectal gland that revealed the role of the gland in the regulation of salt homeostasis in elasmobranchs. He showed that the gland secreted an almost pure solution of sodium chloride that was isosmotic with blood, contained little urea, and that the volume of secretion tended to be oscillatory. He used sympathetic and parasympathetic agents, hormones, and pharmacological agents to try to activate the gland but could not do so. Crucially, he observed that the administration of a volume load of a variety of solutions induced consistent and reproducible stimulation of the secretion by the rectal gland. He concluded that the secretion by the gland was under humoral control but could not define the agent. Palmer developed a preparation of isolated perfused rectal glands, which was then taken up by Hayslett, which proved to be essential for the study of the function and regulation of the secretion by the gland. Their initial investigations established that the gland secreted chloride against an electrical and chemical gradient, but the process by which it did so could not be ascertained because the preparation had problems. Some of the glands did not work, and in those that worked, the gland secretion declined progressively with time. At that time J. Stoff decided to add theophylline and dibutyryl cyclic AMP to the solution perfusing the glands and discovered that both activated the gland. He had found that the gland was under hormonal control by an unknown hormone that activated adenylate cyclase in the rectal gland.