Bayliss and Starling

Bayliss and Starling [ 104] described the peristaltic reflex of small intestine in 1899. This enterically controlled reflex elicits a contraction oral to and a relaxation distal to a segmental distension, resulting in the movement of contents in the aboral direction [104], The peristaltic reflex is funda-... 

Q10 Normally, pancreatic secretion is stimulated by eating. The factors involved are both nervous and hormonal. Pancreatic secretion is increased by vagal (parasympathetic) stimulation and inhibited by sympathetic stimulation. Cholecystokinin (CCK), released from the wall of the duodenum, stimulates pancreatic juice, which is rich in enzymes. Secretin (the first hormone to be discovered, by Bayliss and Starling), which is also produced in the duodenum, stimulates a pancreatic fluid with a high bicarbonate content. 

Pawlow first established the correlation which exists between the gastric and pancreatic secretions. According to him, this second secretion was due to a nervous reflex, resulting from innervation produced by various substances of the chyme, notably its acidity. This opinion is no longer accepted by physiologists. Bayliss and Starling have, in fact, shown experimentally that the nervous system does not intervene at all in the pancreatic secretion, but that this is caused solely by a humoral route, under the action of a special substance, secretin, which is contained in the intestine and which normally, in the course of digestion, is distributed in the blood and directly excites the cells of the pancreas. 

Two hormones are involved in pancreatic secretion secretin and pancreozymin. In the early 1900 s, researchers observed that dilute hydrochloric acid placed in the duodenum stimulated pancreatic secretion. Bayliss and Starling prepared an acid extract of the intestinal mucosa, injected it, and observed pancreatic stimulation. This was the first instance of a nonnervous transmission of a stimulus. Bayliss and Starling boldly coined the word hormone to refer to this type of new agent and called the first hormone secretin. ... 

As a teacher of physiology at St. Bartholomew s Hospital Medical School in London, John Sydney Edkins was well aware of Bayliss and Starling s discovery. " He was also aware of the problem of the control of gastric secretion, for he had contributed a chapter on Mechanisms of Secretion of Gastric, Pancreatic, and Intestinal Juices to Schafer s Text-book of Physiology, published in 1898. ... 

Bayliss and Starling s results made Edkins wonder whether there is a gastric secretin. By 18 May 1905 he had obtained enough evidence to make a preliminary communication to the Royal Society.When he described the properties of the active principle which may be called gastrin, he coined a name that was a little but not much more specific than secretin. Edkins published his complete paper in a 1906 issue of the Journal of Physiology. 

Pavlov radically changed his opinion about the new fact discovered by the English physiologists probably in the fall or in the winter of 1902-3 after reading Bayliss and Starling s... 

Pavlov accepted Bayliss and Starling s proof of hormonal control of pancreatic secretion, but he was by no means willing to give up nervous control as well. As part of what Babkin called Pavlov s effort to rehabilitate the role of the nervous system... 

Nevertheless, the concept of a hormonally mediated regulatory system in the gastrointestinal tract remained a considerable issue for Pavlov and the supporters of the nervism doctrine. In his biography of Pavlov, Babkin noted the turbulence generated by the observations of Bayliss and Starling as well as Edkins. 

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