ABSTRACT
Ivan Pavlov asked about the relationship between the technician and the dog. Pavlov realized that the dog salivated in the technician’s presence because he was expecting food and stopped secreting when he left because his expectations were dashed. He was not salivating because food was in his mouth, the process Pavlov had been studying, but in anticipation of eating. Using his famous bell in place of the technician, Pavlov explored the nature of the conditioned response. Ernest Starling’s messy suspension had made an absolute mess of Pavlov’s sense of an all-controlling nervous system. In the late 19th century, the study of nervous reflexes was a central pursuit of many physiologists. Two physiologists, Starling and his brother-in-law William Bayliss, discovered a means of biological regulation that did not involve the nervous system. They found that a substance made in one tissue could affect the action of another remote tissue by passing through the bloodstream.
