THE CHEMISTRY OF THE ANIMAL BODY. 1009 



sugar, for example. So perhaps, in levulose-fermentation the first step may 

 be conversion into glycogen or the anhydride of dextrose. Cremer maintains 

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

 producers. 



Dextrins. These have been described under starch. 



H H OHH 



d-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 GENEEAL. 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 fed with fat, and 1 to 

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

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

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

 amount decomposed in starvation. The above shows what is well known, that 

 sugar spares proteid from decomposition more than fat does. E. Voit 2 states 

 these two propositions : (1) The part played by these several food-stuffs in the 

 total metabolism depends on the composition of the fluid feeding the cell. 

 The greater the amount of one of these food-stuffs, the greater its decompo- 

 sition and the less the decomposition of the others, so long as the total decom- 

 position suffers no change. (2) The several food-stuffs do not act wholly on 

 account of their quantity in the fluid surrounding the cell, but especially accord- 

 ing to the chemical affinity of the cell-substance for them individually. First 

 in this regard comes proteid, then carbohydrates, and lastly fat. 



The excessive proteid decomposition in diabetes is due to the non-combus- 

 tion of the proteid protecting sugars 3 and the same is true in fever where a 

 small supply of carbohydrates reaches the blood. 4 



1 E. Voit and Korkunoff: Zeitschri/t fur Biologie, 1895, Bd. 32, p. 117. 



2 Op. tit., pp. 128 and 135. 3 Lusk: Zeitschrift filr Biologic, 1890, Bd. 27, p. 459. 

 4 May : Ibid., 1894, Bd. 30, p. 1. 



64 



