748 SPECIAL PHYSIOLOGY. 



the proportion to be about 7 per cent, with a pure animal diet, 14.5 

 per cent, with meat and sugar, and 17 per cent, with a purely vegeta- 

 ble diet. It is believed that the glycogen found so abundantly in the 

 muscles of the embryo, the inosite formed in the muscles after birth, 

 and the small quantity of glycogen which they contain after the liver 

 has commenced its glycogenic office, are also derived from the decom- 

 position of albuminoid substance into glycogen, and some oxidizable 

 nitrogenous body, such as creatin or creatinin. 



The use of the glycogenic function of the liver is supposed to be 

 that of continuously supplying an easily oxidizable material for the 

 purposes of maintaining animal heat and motion. Sugar is a very 

 unstable element in the presence of oxygen with albuminoid sub- 

 stances, such as are found in the blood. As already stated, the 

 quantity of sugar found in arterial blood, that is, in the blood which 

 has passed through the lungs, is much smaller than that in the hepatic 

 venous blood. Besides undergoing oxidation, like the sugar of the 

 food, so as to form carbonic acid and water, the liver-sugar may also 

 be capable of transformation, through the assimilative force of some 

 of the animal tissues or organs, into fatty matter, or some other sub- 

 stances necessary to the living economy. 



The sugar may likewise act as a solvent of the carbonate and phos- 

 phate of lime in the blood. It has also been said to aid in the decom- 

 position of albuminoid into oleaginous or other compounds. 



When animals are covered with varnish, which arrests the cuta- 

 neous transpiration, and interferes with the respiratory changes and 

 the development of animal heat, both the sugar of the hepatic blood, 

 and the glycogen of the liver, soon disappear; but, by then employing 

 artificial warmth, they may be again formed. In hibernating ani- 

 mals, in which the respiratory process is also reduced to a minimum, 

 the formation of sugar continues, but its oxidation, after it passes into 

 the circulation, is imperfectly carried on, or entirely ceases, so that it 

 accumulates in the blood, and even appears in the urine. So, too, in 

 the disease known as diabetes mellitus, the sugar found in that excre- 

 tion is supposed to depend upon the accumulation of sugar, probably 

 of liver-sugar in the blood; for, in such cases, other secretions and ex- 

 cretions also exhibit traces of that substance. That the sugar excreted 

 by the kidneys in diabetes is not formed in those organs, is certain ; 

 and it has been noticed that if the blood contain Jd of a grain of sugar 

 in 100 grains, this substance is no longer completely consumed, or ox- 

 idized in the combustive processes of the economy, but appears in the 

 various secretions and excretions, most abundantly in that from the 

 kidneys. In the diabetic condition, not only may the sugar formed 

 in normal quantity accumulate, from not undergoing decomposition, 

 but the liver may generate more sugar than usual. 



A temporary and remediable diabetes may occur from the undue 

 ingestion of sugar, or sugar-forming substances, with the food. More- 

 over, many medicinal agents appear to determine an increased activity 

 of the glycogenic function of the liver, producing an artificial diabetes ; 

 such are morphia, strychnia, and phosphoric acid, in large quantities. 

 (Pavy.) Asparagus has a similar effect; so likewise has the injection 



