550 AUyORMALITIES IX METABOLISM 



Normal serum binds about 75 per cent, of its volume of CO,, whereas 

 in acidosis it may bind but 20 per cent. (Van Slyke). 



DIABETIC COMA 23 



In man, poisoning with inorganic acids, as in the experiments cited 

 above, is a rare occurrence, but not infrequently acid intoxication re- 

 sults from the presence of undue quantities of organic acids pro- 

 duced in metabolism. Tlie most striking example of this is the coma 

 of diabetes, in which the asphyxia without cyanosis, dependent upon 

 failure of the blood to carry CO,, is sometimes strikingly similar to 

 that observed in experimental animals poisoned with acids. In dia- 

 betic coma the acid intoxication is due chiefly to the accumulation in 

 the blood or tissues of large quantities of (3-oxyhiityric acid. Associ- 

 ated with it, in smaller quantities, are usually found diacetic (aceto- 

 acetic) acid and acetone, which are chemically so closely related that 

 it has been generally considered that they are derived from the oxy- 

 butyric acid, as follows : 



y8-oxybutyric acid is — 



CH3 — CHOH— CH,— COOH, 



and by oxidation this readily forms — 



CH3— CO— CH„— COOH, 



which is diacetic acid (being two molecules of acetic acid united to 

 each other, as follows) : 



CH3— CO— I OH— H I — H,C— COOH. 



Diacetic acid is, in turn, readily deprived of its carbon dioxide, forming 

 acetone, 



CH3— CO— CH3. 



All these reactions are easily accomplished in the laboratory^ and there 

 seemed to be reason for believing that they may normally occur in the 

 same way in the animal body. Wakeman and Dakin,-'^ and others, 

 however, found evidence that the liver cells may also reduce diacetic 

 to /8-oxybutyric acid, and it seems probable that this is the usual 

 direction of the reaction, which they have found to be produced by a 

 specific enzyme. Ilurtley "^ concludes that the reduction of aceto- 

 acetic acid to oxybutyric acid is accomplished b}^ the body under 

 ordinary conditions far more readily than the oxidation of oxybutyric 

 to aceto-acetic acid. Marriot "^^ gives the following scheme as indi- 

 cating the normal path of fatty acid catabolism: 



d — oxvhutric acid 



Fatty acid y{ I'.utyric aci.l( ?) ) VAccto-acctic acid )./< '••^'Klilv burned) 



1 — oxynutric acid 

 (dillicultly hurned) 



27 Jour. Biol. Chom., inon (6). 373; 1010 (8), 105. 

 2-a.T<mr. Biol. Chem., 1914 (18), 241. 



