PRODUCTION OF SUGAR IN THE LIVER. 467 



culiarities of liver-sugar. It resembles glucose, or the sugar resulting from the digestion 

 of starch, in its composition. This sugar, like glucose, responds promptly to all of the 

 copper-tests, and it undergoes transformation into melassic acid on being boiled with an 

 alkali. One of its most marked peculiarities is that it ferments more readily than any 

 other variety of sugar ; and another is that it is destroyed in the economy with extraor- 

 dinary facility. This fact has been illustrated by the following ingenious experiment : 

 Bernard injected under the skin of a rabbit a little more than seven grains of cane- 

 sugar dissolved in about an ounce of water, and he found sugar in the urine. Under 

 the same conditions, he found he could inject seven grains of milk-sugar, fourteen and 

 a half grains of glucose, twenty-one and a half grains of diabetic sugar, and nearly 

 thirty grains of liver-sugar, without finding any sugar in the urine ; showing that the 

 liver-sugar is consumed in the organism more rapidly and completely than any other sac- 

 charine principle. 



Mechanism of the Production of Sugar in the Liver. When Bernard first described 

 the glycogenic function of the liver, he thought that the sugar was produced from nitro- 

 genized principles, in some manner which he did not attempt to explain. Subsequent 

 discoveries, however, have led to conclusions entirely different. 



In 1855, Bernard first published an account of his remarkable experiment showing 

 the post-mortem- production of sugar. After washing out the liver with water passed 

 through the vessels until it no longer contained a vestige of sugar, it was allowed to 

 remain at about the temperature of the body for a few hours and was then found to con- 

 tain sugar in abundance. This experiment we have already referred to, and it is one 

 that we have frequently verified. Bernard explained the phenomenon by the supposition, 

 subsequently shown to be correct, that the liver contains a peculiar principle, slightly 

 soluble in water and capable of transformation into sugar. 



Glycogenic Matter. In its composition, reactions, and particularly in the facility with 

 which it undergoes transformation into sugar, glycogenic matter bears a very close 

 resemblance to starch. It is described by Pavy under the name of amyloid matter, a 

 name which is applied to it, also, by Rouget. It is insoluble in water, and, by virtue 

 of this property, it may be extracted from the liver after the sugar has been washed 

 out. The following is the method for its extraction proposed by Bernard : 



The liver of a small and young animal, like the rabbit, in full digestion, presents the 

 most favorable conditions for the extraction of the glycogenic matter. The liver is 

 taken from the animal immediately after it is killed, is cut into thin slices, and thrown 

 into boiling water. When the tissue is hardened, it is removed and ground into a pulp 

 in a mortar. It is then boiled a second time in the water of the first decoction, strained 

 through a cloth, and the opaline liquid which passes through is made into a thin 

 paste with animal charcoal. The paste is then put into a displacement-apparatus, the 

 end of which is loosely filled with shreds of moistened cotton. By successive wash- 

 ings, the paste is exhausted of its glycogenic matter, leaving behind the albuminoid 

 and coloring matters. The whitish liquid, as it flows, is received into a vessel of abso- 

 lute alcohol, when, as each drop falls, the glycogenic matter is precipitated in white 

 flakes. This is filtered and dried rapidly in a current of air. If the alcohol be not 

 allowed to become too dilute, the matter when dried is white and easily pulverized. 

 The substance thus obtained may be held in suspension in water, giving to the liquid a 

 strongly opaline appearance. It is neutral, without odor or taste, and presents nothing 

 characteristic under the microscope. It reacts strongly with iodine, which produces 

 a dark-violet or chestnut-brown color, but rarely a well-marked blue. It presents none 

 of the reactions of sugar and is entirely insoluble in alcohol. It is changed into sugar 

 by boiling for a long time with dilute acids, and this conversion is rapidly effected 

 by the saliva, the pancreatic juice, and a peculiar ferment found in the substance of 



