CHEMICAL MECHANISMS OF SECRETION 291 



have traced it as far as possible towards the periphery, and con- 

 clude that it acts in all probability directly as a chemical excitant 



FIG. 5. ACTION OF ACID EXTRACT OF BOILED AND WASHED Mucous 

 MEMBRANE OF DUODENUM. 



A, Blood-pressure; B, drops of pancreatic juice; C, drops of bile; D, time 

 tracing. (Bayliss and Starling.) 



FIG. 6. ACTION OF ACID EXTRACT OF Mucous MEMBRANE OF DUODENUM 



WHICH HAS BEEN DRIED AFTER DEHYDRATION BY ALCOHOL. 



A, Blood-pressure; B, drops of pancreatic juice; C, injection signal; D, time 

 tracing. (Bayliss and Starling.) 



upon the secreting cells of the pancreas. It is impossible with our 

 present experimental methods to exclude a possible action upon 



