HISTORY OF ENDOCRINE DOCTRINE 



59 



formed into some other substance. If the locus of this transformation 

 could be discovered and its activities inhibited, an artificial diabetes might 

 be produced by the induction of excess of sugar in the blood. On feeding a 

 dog on rich sugar diet and killing it at the height of digestion, he found the 

 hepatic veins loaded with dextrose, and although this looked at first as if 

 the liver was not the site of transformation, Bernard (a) changed his mind 

 when he found that the blood from the hepatic vein of another dog fed 

 upon meat only (a sheep's head) was also loaded with grape sugar. Thus, 

 it appeared that the liver is a sugar manufacturing plant,, and that its 

 sugar producing or glycogenic function is in the nature of an internal secre- 

 tion, a view which he confirmed by many 

 varied experiments, publishing his re- 

 sults in 1848-50. About the same time 

 Bernard discovered that a puncture in 

 the region of the fourth ventricle of the 

 brain in the dog will produce a tempor- 

 ary glycosuria (1849) or medullary 

 diabetes mellitus. The later experi- 

 ments of E. Frank (1912) and of Har- 

 vey Cushing (d) and his associates 

 (1913) indicate that there is also a poly- 

 dipsia and polyuria deriving from the 

 pituitary body. As a simple decoction of 

 the liver substance was always found to 

 contain dextrose, the next step was to 

 ascertain how the liver produced this 

 substance at the expense of the materials 

 sent from the alimentary canal. After 

 perfusing a freshly excised liver until 

 the wash water from the hepatic vein 

 contained no sugar, Bernard found that, if the liver were left in 

 a warm place for a few hours, a subsequent perfusion would once more 

 come out loaded with sugar, and, although this property of the 

 hepatic tissue could be destroyed by boiling, the sugar producing power 

 could be restored by adding to a decoction of the boiled liver a small 

 quantity of fresh liver infusion. From this he inferred that the glycogenic 

 function is, in effect, a fermentative process, and that its agency is a kind 

 of starch. In 1855, he succeeded in obtaining this glycogenic substance in 

 the form of a dry powder, which could be converted into dextrose by fer- 

 mentation, although it did not itself respond to the sugar tests. In 1857, 

 by his potash-alcohol process, Bernard (c) obtained it in the pure state as 

 "glycogen." In Bernard's view, glycogen was the ''secretion interne" of 

 the liver, over and above its ordinary external secretion, bile. It was the 

 fact that glycogen could be seen, touched, tasted and experimented upon, 



Fig. 7. Claude Bernard 

 (1813-1878) 



