[Endocrinology from the viewpoint of the zoologist]

The argument is presented that the scientific discipline of endocrinology originated in experimental zoology. The identification of the first ductless glands and the characteristization of their products required the proof that their excision caused recognizable changes which could be reversed by replacement therapy. This could only be obtained from animal experimentation. Zoologists contributed, but an important factor was the tradition of zoology in the medical curriculum, especially in Middle Europe from where sprang the immortal names of Berthold, Langerhans, Knauer, von Halban, Fraenkel, Biedl, and many others.