CHEMICAL BASIS OF THE ANIMAL BODY. 107 



substance and was named by him cerebrose, is really identical with 

 galactose l . 



Galactose is fermentible with yeast, but less readily so than is 

 dextrose. 



4. Glycuronic acid. C 6 H 10 7 . [COH - (CH . OH) 4 - COOH]. 



This acid was first obtained as a compound, campho-glycuronic acid, 

 in the urine of dogs after the administration of camphor 2 , and subse- 

 quently as urochloralic acid after the administration of chloral 3 . Since 

 then it has been found in urine as ethereal or glucoside-like compounds 

 with an extensive series of members of the fatty or aromatic series after 

 the introduction of the appropriate substances into the animal body 4 . 

 It is probable that traces of compounds of this acid occur normally in 

 urine since this excretion is usually slightly Isevo-rotatory and it is 

 known that indol and skatol which are formed in the alimentary canal 

 readily reappear in the urine .as compounds of glycuronic acid, viz. 

 indoxyl- and skatoxyl-glycuronic acid, when introduced into the body. 

 The compounds of glycuronic acid are all Isevo-rotatory and some of 

 them reduce metallic salts on boiling and may hence lead to errors in 

 the determination of sugar in urine. 



Glycuronic acid does not occur in the free state in the animal body. 

 Chemically it is closely related to dextrose; when oxidised with bro- 

 mine it yields saccharic acid 5 C 6 H 10 O 8 . [COOH - (CH . OH) 4 - COOH] 

 an acid which is also readily obtained by the oxidation of dextrose with 

 nitric acid. Saccharic acid can be converted into glycuronic acid by 

 reduction with sodium amalgam 6 . Like dextrose glycuronic acid is 

 dextro-rotatory but to a less extent, (a) D = +19'4, reduces Fehling's 

 fluid to the same extent as does dextrose and forms with phenyl- 

 hydrazin a yellow crystalline compound which melts at 114-^-115. 

 The acid is known only as a syrup soluble in alcohol and water. 

 When boiled in the latter solvent it loses a molecule of water and 

 yields an anhydride (lactone) C 6 H 8 6 which is crystalline, insoluble 

 in alcohol, soluble in water, dextro-rotatory and reduces Fehling's fluid 

 powerfully. 



The formation of the compounds of glycuronic acid to which 



1 Thierfelder, Zt. f. physiol Chem. Bd. xiv. (1889), S. 209. Brown and Morris, 

 Jl. Chem. Soc. Vol. LVII. (1890), p. 57. 



2 Schmiedeberg u. Meyer, Zt. f. physiol. Chem. Bd. in. (1879), S. 422. 



3 v. Mering, Ibid. Bd. vi. (1882), S. 480. 



4 For very full list of the various substances which when introduced into the 

 body reappear in the urine as paired compounds with glycuronic acid and for 

 references to date (1890) to the literature of the subject see Neubauer u. Vogel, 

 Harnanalyse, Ed. ix. 1890, p. 116. 



5 Thierfelder, Zt. f. physiol. Chem. Bd. xi. (1887), S. 388. See also Bd. xm. 

 (1889), S. 275. 



6 Fischer u. Piloty, Ber. d. d. chem. Gesell. Jahrg. xxiv. (1891), S. 521. 



