THE CHEMISTRY OF THE ANIMAL BODY. 567 



tissue, while excess of sugar is stored iu the muscles and especially in the liver- 

 cells in the less combustible and less diffusible form of glycogen. About one- 

 half of the total quantity of glycogen is found in the muscles, the remainder 

 in the liver, where it may even amount to 40 per cent, of the dry solids. 

 When the blood becomes poor in sugar, the store of glycogen is drawn upon to 

 such an extent that in hunger the body loses the larger part of its glycogen. 

 Muscular work likewise causes the rapid conversion of glycogen into sugar. 

 The sources of glycogen are certain ingested carbohydrates, and also the 

 dextrose derived from proteid. If large quantities of proteid be fed, 

 glycogen may be stored. If dextrose, levulose, or galactose (or anything 

 which produces these, e. g. cane-sugar, maltose, milk-sugar) be fed, there 

 may be a direct conversion of these sugars into glycogen. Cremer maintains 

 that the pentoses are burned in the body, but are only indirectly glycogen- 

 producers in the sense of sparing other sugar from destruction, which may 

 be used to form glycogen. 



Dextrins. — These have been described under starch. 



H H OHH 



^-Glucuronic Acid, or Glycuronic Acid, HOOC C C C C C HO. 



OH OHH OH 

 — Obtained by reducing d-saccharic acid with nascent hydrogen. After feed- 

 ing chloral hydrate, naphthalin, camphor, terpentine, phenol, ortho-nitrotoluol, 

 and other bodies, they appear in the urine (usually having been first converted 

 into alcohol) in combination with glycuronic acid. Urochloralic acid, naphthol- 

 glycuronic acid, campho-glycuronic acid, terpene-glycuronic acid, etc., all rotate 

 polarized light to the left. It seems that these ingested substances unite in the 

 body with the aldehyde group of dextrose, at the same time protecting all but 

 one group of the dextrose molecule from further oxidation (Fischer). Glycu- 

 ronic acid, which is easily separated by hydrolysis from its aromatic combina- 

 tion, itself rotates polarized light to the right, reduces alkaline copper solutions, 

 and might be confounded with dextrose except that it does not ferment with 

 yeast. Glycuronic acid is likewise found in the urine after administration of 

 curare, morphine, and after chloroform-narcosis, perhaps paired with aromatic 

 bodies formed in the organization. 



Combustion in the Cell, in General. — Experiments 1 show that taking 

 the proteid decomposition in the starving dog as 1, it is necessary to feed three 

 to four times that amount of proteid taken alone in order to attain nitrogenous 

 equilibrium, 1.6 to 2.1 times that amount of proteid when i'ed with fat, and 1 to 

 1.2 times that amount when led with carbohydrates. The physiological proteid 

 minimum is in these eases never less than the amount required in starvation. 

 Only after feeding gelatin with proteid may the proteid led be below the 

 amount decomposed in starvation. The above show- wliai is well known, that 

 sugar spares proteid from decomposition more than I'at does. E. Voil J States 



1 E. Voit and Korkunoff: Zetisehrifl fir Biologic, 1895, Bd. 32, S. 117. 



2 Op. cit, S. 128 and 135. 



