118 GLANDS IN HEALTH AND DISEASE 



the blood, and stored there in the form of glyco- 

 gen. Whenever the body needs carbohydrates for 

 its various energy purposes, the glycogen is decom- 

 posed into glucose, and this substance is sent to the 

 various tissues where it is "burnt" or "oxidized" 

 into carbon dioxide and water. 



The liver a ductless gland. You will remember 

 that we defined a ductless gland as one producing 

 a secretion which passed directly into the blood, 

 and which secretion contained a something (hor- 

 mone) that influenced other organs to various 

 modes of activity. Can the liver be viewed as a 

 ductless gland? It certainly produces an internal 

 secretion in the sense of being able to take material 

 (simple carbohydrates) from the blood, converting 

 it into other products (first into glycogen and then 

 into glucose), and passing the glucose directly into 

 the blood. But where is the hormone, -the substance 

 that influences the activity of other organs? We 

 must look to the pancreas for such a substance. 



Claude Bernard. At any rate, the glycogen 

 function of the liver * is of extraordinary interest, 



*Not only does the liver manufacture glycogen, but it also 

 makes urea from ammonia and carbon dioxide. This urea is 

 carried away by the blood and finds its way into the urine. 80 

 per cent, of the total nitrogenous products (representing sub- 

 stances derived from protein) in the urine is in the form of urea. 

 The formation of urea, like that of glycogen, is evidence of the 

 internal secretory mechanism of the liver. This by no means 

 exhausts the functions of the liver, a veritable storehouse of 

 wonders. 



It should be remarked at this point that a rigid definition of 



