128 GLANDS IN HEALTH AND DISEASE 



and sent to the cells. One of these liquids is elab- 

 orated by the intestine itself; another, the bile, 

 comes from the liver ; and the third, the pancreatic 

 juice, from the pancreas. 



The last two reach the intestine by means of 

 ducts or tubes. They represent typical "external 

 secretions," in contradistinction to the "internal 

 secretions" that we have studied, and that flow di- 

 rectly into the blood. 



The hormone in the intestine. Now the ques- 

 tion arises, why whenever food enters the intestine, 

 and only then, do bile and pancreatic juice also 

 begin to flow into it? The easiest answer, the most 

 obvious one, is that there is a nervous mechanism 

 involved ; that the brain correlates the activities of 

 these organs. Such a theory had a distinguished 

 supporter in the person of Pavlov, the Kussian 

 physiologist, whose present plight has been so 

 graphically described by H. G. Wells, the novelist 

 who is also a scientist. We are about to show that 

 Pavlov's theory of brain interference is untenable ; 

 that all nerve connections between the brain and 

 intestine can be severed without stopping the flow 

 of pancreatic juice; that the chief factor that brings 

 about this coordination at least in so far as the 

 flow of pancreatic juice is concerned, and, to a less 

 extent, the bile, is a hormone elaborated by the 

 small intestine; that this hormone is produced 

 whenever the acid food from the stomach finds its 



