184 CHEMICAL MECHANISMS OF SECRETION 



experiment, and during its course were anaesthetised with A.C.E. 

 mixture. In order to keep the condition of the animals constant 

 during the experiment, artificial respiration was resorted to, and 

 a constant depth of anaesthesia was attained by placing the 

 anaesthetising bottle in the air circuit ; this procedure is especially 

 necessary when the vagi have been cut. The animals in the 

 earlier experiments had not been fed for a period of eighteen to 

 twenty-four hours, but in later experiments it was shown that 

 secretin is active no matter what may be the state of digestion. 

 In order 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 0*4 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 



