132 GLANDS IN HEALTH AND DISEASE 



fails to cause a flow of pancreatic juice, and since 

 hydrochloric acid alone is no better, but since when 

 the two are mixed we do get a response, Professors 

 Bayliss and Starling have advanced the hypothesis 

 that in its original form the secretin is in an in- 

 active state the "pro-secretin" state they term it; 

 and that the hormone becomes active only when 

 the acid converts the pro-secretin into secretin. 

 The function of the acid coming from the stomach, 

 then, is to convert the inactive into an active hor- 

 mone. The fact that solutions containing secretin 

 can be boiled without destroying the hormone sug- 

 gests that this hormone and others? are quite 

 distinct from either vitamines or enzymes, both of 

 which are quite susceptible to increases in tempera- 

 ture. 



An objection to the work of Bayliss and Starling. 

 The Italian physiologist, Luciani, has criticized 

 the work of the English scientists. He writes : 1 

 "Popielski and his pupils have recently published 

 a series of experiments and conclusions which com- 

 pletely refute the secretin theory. Popielski states 

 that the substance extracted after the extraction 

 of the duodenal mucosa with hydrochloric acid is 

 not specific, but may, on the contrary, be obtained 

 by simple hydrolysis, from any glandular, muscu- 

 lar, or even nervous tissue. . . . But the follow- 

 ing is the most cogent of PopielskPs arguments. 



1 Human Physiology, Volume 2. 



