130 OXALIC ACID, 



do 1 , it is most probable that the lactic acid is a product of the breaking 

 down of the complex (nitrogenous) molecule whose decomposition is the 

 source of the energy which the muscle can set free 2 . Glycogen is accord- 

 ing to this view to be regarded rather as a convenient accessory to the 

 activity than as either the basis of this activity or of the lactic acid 

 which arises during the activity. 



3. Ethylene-lactic acid. CH 2 (OH) . CH 2 . COOH. 



This acid has been usually described as accompanying sarcolactic 

 acid in extracts of muscles and as being isolable from this by taking 

 advantage of the varying solubilities of the zinc salts of the two acids 3 . 



More recent researches have however made it probable that what 

 has usually been described as ethylene-lactic acid, obtainable from 

 muscle-extract, is really acetyl-lactic acid, CH 3 . CH (C 2 H 3 O 2 ) COOH, 

 the true ethylene-lactic acid being hydracrylic acid, which does not 

 occur in the animal body 4 . 



Hydroxy-butyric acid 5 . CH 3 . CH (OH) . CH 2 . COOH. 



This acid is the next homologue to the lactic acids in the glycolic 

 series. It is frequently found in the urine of acute diabetes, usually 

 accompanied by aceto-acetic acid [CH 3 . CO . CH 2 . COOH]. The pure 

 acid is sirupy and Isevo-rotatory, (a) D = 23*4. For its separation from 

 urine and estimation see Kiilz 6 and Stadelmann 7 . 



OXALIC ACID SERIES. 



Oxalic acid. (CO. OH), 



This acid does not occur in the free state in the human body. Cal- 

 cium oxalate, however, is a not unfrequent constituent of urine, and 

 enters into the composition of many urinary calculi, the so-called 

 mulberry calculus consisting almost entirely of it, and it is very 

 commonly found in urinary deposits. As ordinarily precipitated from 

 solutions of calcium salts by the addition of a salt of oxalic acid, the 

 calcium oxalate is usually amorphous. To obtain it in the crystalline 

 form dilute solutions of the two reagents must be allowed to mix very 

 slowly, as by diffusion. In urine the case is different ; the oxalate is at 



1 Heidenhain, Mechanische Leistung Warmeentwick. u. Stoffumsatz bei der Muskel- 

 thdtigkeit. Leipzig, 1864. Banke, Tetanus. Leipzig, 1865. Hermann, Unters. li. d. 

 Sto/wechsel d. Muskeln. Berlin, 1867. 



2 Cf. Werther, loc. cit. S. 85. Halliburton, Jl. Physiol. Vol. vm. (1887), p. 154. 



3 Wislicenus, Ann. d. Chem. u. Pharm. Bd. CLXVII. (1873), S. 302. 



4 Siegfried, Ber. d. d. chem. GeselL Jahrg. 1889, S. 2711. 



5 See Neubauer u. Vogel, Analyse d. Harns, 1890, S. 110. 



6 Zt.f. Biol. Bd. xxm. (1887), S. 329. 



7 Ibid. S. 456. 



