HOW THE GLANDS WERE DISCOVERED 45 



was evident that the stimulus to the pancreas was carried by 

 way of the blood stream. That the stimulating substance was 

 not the acid itself, was shown by the failure of the reaction to 

 occur when the acid was injected directly into the blood stream. 

 Since there was this difference in the effects between acid in the 

 intestine and acid in the blood, it was manifest that the active 

 substance must be some material elaborated in the intestinal 

 mucous membrane under the influence of the acid. So they 

 scraped some of the lining of the bowel, rubbed it up with acid, 

 and injected the filtered mixture into the blood. They were re- 

 warded by a flow of pancreatic juice greater in amount than any 

 obtained in their other experiments. From the filtered mixture 

 they isolated in an impure form, a solid substance which, when 

 introduced into the circulation, has a similar action. To this, of 

 which the exact chemical make-up is as yet an unknown, they 

 gave the name secretin. 



Secretin and its properties they used to generalize as a per- 

 fectly direct and amply demonstrable example of an internal 

 secretion. Metaphors are no less valuable in physiology than in 

 poetry. They declared that the internal secretions appeared to 

 them to be chemical messengers, telegraph boys sent from one 

 organ to another through the public highways, the blood (really 

 more like a moving platform). So they christened them all 

 hormones, deriving the word from the Greek verb meaning to 

 rouse or set in motion. As a science is a well-made language, a 

 new word is an event. It sums up details, economizes brain- 

 work and so is cherished by the intellect. The study of the 

 internal secretions has advanced by leaps and bounds since it 

 became convenient to speak of them as hormones. Withal, the 

 brilliant work of Bayliss and Starling stands as the third great 

 foundation stone, the first Claude Bernard's and the second 

 Brown-Sequard's, in the architecture of the modern concepts of 

 the internal secretions. 



