CHEMICAL MECHANISMS OF SECRETION 289 



to avoid shock and to keep up the temperature, the animal was 

 immersed in a bath of warm physiological saline throughout the 

 experiment ; the level of the fluid was above that of the abdominal 

 wound, so that the intestine was bathed with the warm fluid. 

 The arterial pressure was always recorded by means of a mercurial 

 manometer connected with the carotid artery in the usual way. 

 The pancreatic juice was obtained by placing a cannula in the 

 larger duct which enters the duodenum on a level with the lower 

 border of the pancreas. To the cannula was connected a long glass 

 tube filled at first with physiological saline ; the end of this tube 

 projected over the edge of the bath so that the drops of the secretion 

 fell upon a mica disc cemented to the lever of a Marey's tambour; 

 this was in connection by means of rubber tubing with another 

 tambour which marked each drop upon the smoked paper of the 

 kymograph. A time tracing was taken showing intervals of ten 

 seconds, and an injection signal was arranged to indicate the 

 point at which acid was injected into the intestine, or a preparation 

 of secretin into a vein, in which a venous cannula had been placed 

 in the usual way. 



The authors first confirmed the results of previous experi- 

 menters as to the effects of injection of acid into the duodenum 

 or jejunum, and found that the result of injecting from 30 to 50 c.c. 

 of 04 per cent, hydrochloric acid into the lumen of the duodenum 

 or jejunum is to produce, after a latent period of about two minutes, 

 a marked flow of pancreatic juice. This effect is still produced 

 after section of both vagi, section of the spinal cord at the level 

 of the foramen magnum, destruction of the spinal cord, section of 

 the splanchnic nerves, extirpation of the solar plexus, or any com- 

 bination of these operations. 



The next step in the chain of evidence was to test the effect 

 of injection of acid into a loop of the upper part of the intestine 

 after severing the mesenteric nerves. Such a procedure was im- 

 possible for anatomical reasons in the duodenum, but was success- 

 fully carried out with a positive result on a loop of jejunum. 



In this crucial experiment the loop of intestine was completely 

 cut off from all nervous connection with the pancreas, and hence 

 the conclusion is an inevitable one that the effect must be produced 

 by some chemical substance finding its way into the circulation, 

 and then either directly or indirectly stimulating the pancreatic 

 cells. 



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