Hormone

“Following the discovery of secretin [1902], the potent chemical secreted by the intestinal mucosa that triggers the release of pancreatic juice, physiologists quickly became fascinated by the idea that chemicals as well as nerves can provoke physiological events. The new term ‘hormone’ was introduced to specify chemicals serving this function. ‘Hormone’ implied a chemical derived from animal tissues, which had specific physiological effects; the term ‘internal secretion’ on the other hand, suggested an entity whose absence resulted in disease, a hypothetical, rather than a demonstrated entity. Hormones could be isolated in the laboratory and studied by recognized physiological methods. The existence of internal secretions, although implied by clinical observations, could not be proved with the same rigor” (Borell IV, 4-5).