CARBOHYDRATES. 97 



peculiar, fruity odor which was noticed by the older physicians. This is 

 due', as C. Gerhardt x supposed and v. Jaksch 2 has shown, to the presence 

 of acetoacetic acid (CH 3 CO)CH 2 . COOH. Besides this compound acetone 

 CH 3 . CO . CH 3 and, as Minkowski 3 has shown, ^-hydroxy-butyric acid 

 CH 3 CH(OH)CH 2 .COOH, are also present in many cases. All three of 

 these compounds, as a glance at their structural formula? will show, stand 

 in direct relation to one another. Acetoacetic acid is evidently formed 

 by the oxidation of /?-hy droxy-butyric acid : 



* CH 3 .CH(OH) . CH 2 . COOH + O = (CH 3 . CO) CH 2 . COOH + H 2 O 

 /?-hydroxy-butyric acid acetoacetic acid 



From acetoacetic acid, acetone is readily formed by loss of carbon 

 dioxide : 



(CH 3 . CO)CH 2 . COOH = CH 3 . CO . CH 3 + CO 2 

 acetoacetic acid acetone 



The fact that in many cases /?-hydroxy-butyric acid is not found in the 

 urine when the other two compounds are present, is not remarkable, for 

 we can easily understand that in one case the former is oxidized and in 

 another case is not. /?-hydroxy-butyric acid contains, as the above formula 

 indicates (*), an asymmetric carbon atom, i.e., it is optically active; as 

 a matter of fact, the left-rotating form is always eliminated. 



It has been attempted repeatedly to establish the origin of these com- 

 pounds in the urine, and especially their significance as regards disease. 

 It is above all worth mentioning that the occurrence of acetone in the 

 urine (acetonurid) is not peculiar to diabetes. To some extent it has been 

 observed in the urine of many fever patients. Acetone and acetoacetic 

 acid have also been found after long-continued inanition. 4 Acetone is 

 also eliminated in small amounts when healthy individuals are fed exclu- 

 sively with albumin and fat. All of the acetone does not leave the system 

 through the kidneys, but a part is given off by the lungs. The question as 

 to the origin of these so-called acetone bodies 5 has been the subject of 

 considerable controversy. The simplest explanation is that they are in 

 some way directly connected with the disturbance in the metabolism of 

 carbohydrates, 6 for the observation that acetonuria occurs after inanition 



1 Wiener med. Presse, 28, 673 (1865). Cf. Fetters Prager Vierteljahresschrift, 65, 

 81 (1857). Jaksch: Z. physiol. Chem. 7, 485 (1883). 



2 Ber. 15, 1496 (1882). 



3 Zentr. med. Wiss. 242 (1884). Kiilz: Arch, exper. Path. Pharm. 18, 291 (1884); 

 Z. Biol. 20, 165 (1884); 23, 329 (1887). O. Minkowski: Arch, exper. Path. Pharm. 

 31, 183 (1893). Araki: Z. physiol. Chem. 18, 1 (1894). 



4 von Jaksch: Ueber Azetonurie und Diazeturie, Berlin, 1895. Fr. Miiller: Berlin, 

 klin. Wochschr. 428 (1887). 



5 H. C. Geelmuyden: Z. physiol. Chem. 23, 431 (1897). 



6 Cf. F. Maignon: Compt. rend. 140, 1124 (1905). 



