CHAPTER XI. IX 

 PHYSIOLOGY Oh THE DIGESTIVE GLANDS Cont'd 



THE HORMONE CONTROL 



This is exhibited besl in the case of the pancn The crucial experi- 

 111**1 1 1 demonstrating tli;it this yhnid is nol primarily dependenl U] 

 nervous impulses for the control of its activity was performed bj B 

 liss and Starling.- Starting with the well-known fad that the application 

 of weak acid to the duodenal mucous membrane exciti iretion '-i' pan- 

 creatic juice, these workers carefully severed all the 1 i 

 a portion of the duodenum, and found on again applying arid to the muc 

 membrane thai the secretion persisted. To explain this result they postu- 

 lated thai the acid must cause some substance to be liberated Into the 

 blood stream, which carries it to the pancreas, the cells of which it then 

 excites to activity. To tesl this hypothesis they scraped off the mucous 

 membrane of the duodenum and ground it in a mortar with weak hydro- 

 chloric acid i <Mi per cent . and. after boiling the solution so as to coagulate 

 the protein, nearly neutralizing and filtering, they obtained a fluid which. 

 immediately caused a copious secretion of pancreatic juice when injected 

 intravenously. 



Accompanying the secretion, however, a marked fall in arterial hi 1 



pressure was observed, making it possible thai the secretion mighl h 

 been due to a vasodilatation occurring in the pancreatic blood v< 'I o 



eliminate this possibility they prepared an extract that wa the 



depressor substances by extracting intestinal epithelium without any of the 

 submucous tissue. The resulting extract had merely the 

 and produced no fall in blood pressure. This secretagoguary sul 

 they named si <-r< tin. 



Further evidence thai the action of secretin is independent i 

 depressor substances has been obtained by taking advai I 

 that the depressor substance is more soluble in alcohol than tl 

 If an acid decoction of duodenal mucous membrane is poured inti 

 lute alcohol, a precipitate is formed, [f this precipitati 

 in water and reprecipitated several times by absolute alcohol, thei 

 drying a white powder is obtained, which is easily soluble in wi I 



resulting solution injected intravenously lias ;i : 



luit produces no eff< cl on hi I prea Tl i 



