316 



Dr. W. M. Bayliss and Prof. E. H. Starling. [Mar. 21, 



interesting to note that this simultaneous secretion is provided for 

 by the same mechanism by which the secretion of pancreatic juice 

 is evoked. If the flow of bile be determined by measuring the 

 outflow from a cannula placed in the bile duct, it will be found that 

 introduction of acid into the duodenum causes a quickened secre- 

 tion of this fluid. The same increase in the secretion of bile can be 

 produced by injecting solutions of secretin into the blood stream. 

 This influence of secretin on the liver has been fully confirmed by 

 Falloise. This observer has shown that acid extracts of the intestinal 

 mucous membrane cause an increase in the bile secretion most marked 

 when the extract is made from the duodenum and diminishing as the 

 extract is taken from the lower parts of the gut, that from the lower 

 section of the ileum being quite ineffective. 



In some cases the injection of secretin is followed by a secretion of 

 glairy saliva, but this is at once abolished on section of the nerves 

 going to the salivary glands, and is simply a result of the lowering of 

 blood pressure which occurs when any extract of the intestinal mucous 

 membrane is injected into the blood stream. On no other glands of 

 the body has secretin the slightest influence. We must, therefore, 

 regard secretin as a drug-like body having a specific excitatory effect 

 on the secreting cells of the liver and pancreas. 



The discovery of secretin has placed in the hands of physiologists 

 the power of controlling the activity of a gland by purely physio 

 logical means, and we have taken opportunity of the control thus 

 acquired to investigate the exact character of the changes induced in 

 the pancreas under this physiological stimulus. So far as we can tell 

 secretin has no specific influence on any one constituent of the 

 pancreatic juice. When injected it causes secretion of a juice which 

 is normal in that it resembles the juice secreted on entry of food into 

 the duodenum, and contains a precursor of trypsin, amylopsin, and 

 steapsin. Secretin, in fact, appears to cause the pancreatic cells to 

 turn out the whole of the mesostates which they have accumulated 

 during rest in preparation for the act of secretion. If secretin be 

 injected at repeated intervals until the gland will no longer respond to 

 the injection, it is found on microscopic examination that the cells 

 have discharged the whole of their granules. In sections stained with 

 toluidine blue and eosin the whole of the cells stain blue in marked 

 contrast to the normal resting gland, where one-half or two-thirds of 

 the inner margin of the cells is taken up with brilliantly stained red 

 granules. This effect is not produced in all cases. In some animals 

 we have injected secretin at frequent intervals over a period of 

 8 hours, and obtained at the end of the experiment a secretion as 

 vigorous as after the first injection. The pancreas in this case was 

 evidently not fatigued, and on killing the animal and examining this 

 organ microscopically, it was found to give the typical picture of a 



