6 GLANDS IN HEALTH AND DISEASE 



out any help from the brain. 1 Note that one organ 

 of the body the intestine in our example manu- 

 factures a substance which finds its way into the 

 blood stream and affects another organ of the 

 body, the pancreas. Here we have a classical ex- 

 ample of the workings of a ductless gland; for in 

 every gland of the ductless variety a specific sub- 

 stance is manufactured that finds its way into the 

 blood stream and influences another organ or or- 

 gans of the body. The substance so manufactured 

 is called a "hormone" (from the Greek "to excite" 

 or "arouse") or "chemical messenger." The hor- 

 mone in the intestinal wall has been given the 

 name of "secretin" by its discoverers. Without 

 this secretin no pancreatic juice could find its way 

 into the intestine, and without pancreatic juice 

 no digestion of food could take place. 



The small intestine is an example of a tissue 

 which gives rise both to an internal and an ex- 

 ternal secretion. Its internal secretion, the secre- 

 tin, has already been described. But as a matter 

 of fact it also develops a secretion, the intestinal 

 juice, which is carried by ducts to the surface of 

 the intestine, in the same way that salivary or 



1 1 do not want the impression to be conveyed that there is no 

 connection between the hormones on the one hand and the nervous 

 system on the other. As a matter of fact there are connecting 

 links, as the chapter on nervous disorders will attempt to make 

 clear. All I want to point out at this stage is that a particular 

 mechanism, for which the brain is held responsible, can be ex- 

 plained without involving the brain at all. 



