296 SECRETION. 



have been few physiological questions that have attracted so 

 much attention ; and the observations of Bernard were soon 

 repeated, modified, and extended by experimentalists in dif- 

 ferent parts of the world. In 1857, Bernard discovered a 

 sugar-forming material in the liver, analogous in its compo- 

 sition and properties to starch ; and this seemed to complete 

 the history of glycogenesis. 



Shortly after the publication of the glycogenic theory, it 

 was found that other changes were effected in the blood in 

 its passage through the liver, and physiologists then under- 

 stood, for the first time, how glandular organs might pro- 

 duce secretions, and yet not discharge them into excretory 

 ducts ; and this, indeed, pointed the way to the explanation 

 of the function of the ductless glands. It is perfectly correct 

 to say that the liver secretes sugar ; but the secretion, in 

 this instance, is carried away by the blood ; and from this 

 point of view, the liver is a ductless gland. It is evident, 

 therefore, that even after having studied fully the secre- 

 tion and the physiological relations of the bile, we have to 

 consider other glandular functions of the liver, hardly less 

 important. 



Evidences of a Glycogenie Function in the Liver. The 

 proof of the glycogenic function of the liver rests upon the 

 fact, experimentally demonstrated by Bernard, that in all 

 animals, the blood coming from the liver by the hepatic 

 veins contains sugar ; and that the presence of this principle 

 here is not dependent upon the starch or sugar of the food. 

 Bernard assumes to have proven that, in carnivorous ani- 

 mals, never having taken starch or sugar into the aliment- 

 ary canal, except in the milk, there is no sugar in the blood 

 of the portal vein as it passes into the liver ; but, under nor- 

 mal conditions, the blood of the hepatic veins always contains 

 sugar. Having examined the blood from various parts of the 

 body, and made extracts of all the other tissues and organs, 

 Bernard was unable to find sugar in any other situations 



