FORMATION OF SUGAR IN THE LIVER. 333 



have to fulfil in relation to the respiratory process, and 

 without which, such purpose probably could not be pro- 

 perly accomplished, and the substances themselves would 

 be eliminated as foreign matters by the kidneys. 



Then, again, it was discovered by Bernard, and the 

 discovery has been amply confirmed, that the liver pos- 

 sesses the remarkable property of forming glucose or grape- 

 sugar (C 6 Hj O ti ), or a substance readily convertible into 

 sugar, even out of principles in the blood which contain no 

 trace of saccharine or amylaceous matter. In Herbivora 

 and in animals living on mixed diet, a large part of the 

 sugar is derived from the saccharine and amylaceous 

 principles introduced in their food. But in animals fed 

 exclusively on flesh, and deprived therefore of this source 

 of sugar, the liver furnishes the means whereby it may be 

 obtained. Not only in Carnivora, however, but apparently 

 in all classes of animals, the liver is continually engaged, 

 during health, in forming sugar, or a substance closely 

 allied to it, in large amount. This substance may always 

 be found in the liver, even when absent from all other parts 

 of the body. 



To demonstrate the presence of sugar in the liver, a por- 

 tion of this organ, after being cut into small pieces, is j 

 bruised in a mortar to a pulp with a small quantity of) 

 water, and the pulp is boiled with sulphate of soda in order , 

 to precipitate albuminous and colouring matters. The de- 1 

 coction is then filtered and. may be tested for glucose. The 

 most usual test is Trommer's. To the filtered solution an 

 equal quantity of liquor potassro is added, with a few drops 

 of a solution of sulphate of copper. The mixture is then j 

 boiled, when the presence of sugar is indicated by a reddish- 1 

 brown precipitate of the suboxide of copper. 



The researches of Bernard and others, however, have 

 shown that the sugar is not formed at once at the liver, 

 but that this organ has the power of producing a peculiar 

 substance allied to starch, which is readily convertible into 



