Dog technologies on display at Pavlov’s Physiology Division of the Imperial Institute of Experimental Medicine, 1904. Courtesy of Wellcome Institute Library, London
We must painfully acknowledge that, precisely because of its great intellectual development, the best of man’s domestic animals—the dog—most often becomes the victim of physiological experiments.... During chronic experiments, when the animal, having recovered from its operation, is under lengthy observation, the dog is irreplaceable; moreover, it is extremely touching. It is almost a participant in the experiments conducted upon it, greatly facilitating the success of the research by its understanding and compliance.
—Ivan Pavlov, 1893