THE CHEMISTRY OF THE ANIMAL BODY. 989 



it has in its formula an asymmetric carbon atom, 1 it is necessary to assume that 

 it consists of an equal mixture of right and left ethidene lactic acid. On 

 standing with Penicittium glaucum the left lactic acid is destroyed more freely 

 than is the right, and the solution rotates polarized light to the right. 2 



The right ethidene lactic acid, called also sarco- or paru-lactic acid, is that 

 which is found in muscle, blood, in various blood-glands, in the pericardial 

 fluid, and in the aqueous humor. Likewise it is found in the urine after 

 strenuous physical effort, after CO-poisoning, in yellow atrophy of the liver, 

 in phosphorus- poisoning, in trichinosis, and in birds (geese and ducks) after 

 the liver has been extirpated. It is sometimes present in diabetic urine. Para- 

 lactic acid is a normal constituent of the blood and increases in amount after 

 work or tetanus. It accumulates in the dying muscle (rigor mortis), causing 

 the formation of KH 2 PO 4 , which gives the acid reaction and causes coagula- 

 tion. 3 Some believe that free lactic acid itself is present and aids in the coag- 

 ulation. Regarding its origin it has been shown that it increases in amount in 

 the dying muscle without simultaneous decrease in the amount of glycogen. 4 

 On extirpation of the liver in geese, 5 ammonia and lactic acid replace the cus- 

 tomary uric acid in the excreta, and previous ingestion of carbohydrates or of 

 urea will not increase the amount of lactic acid. The lactic acid excreted is 

 proportional in amount to the proteid destroyed and to the ammonia present. 

 It may fairly be concluded that it owes its origin to proteid. 



Hoppe-Seyler 6 says that lactic acid appears in the urine only when there is insufficient 

 oxidation in the body, and attributes its derivation to the decomposition of glycogen. In 

 CO-poisoning Araki 7 finds as much as 2 per cent, of lactic acid (reckoned as zinc lactate) in 

 a rabbit's urine. Minkowski, 8 on the other hand, denies the insufficient -oxidation theory, 

 and maintains that the destruction of lactic acid depends on a specific property of the 



1 An asymmetric carbon atom is one in which the four atoms, or groups of atoms, united to 



CH 3 



it are all different. In lactic acid we find the following grouping, H C OH. The central 



COOH. 



carbon represents the asymmetric atom. Such an arrangement is always optically active. One 

 is able to conceive the arrangement of the atoms in space, according to the above grouping, or 

 CH 3 



as follows : HO C H. This latter represents a different configuration. The two arrange- 



COOH 



mente are optically antagonistic. A mixture of the two is optically inactive. The reader is 

 referred to a text-book on general chemistry for the suggestive illustrations of the tetrahedral 

 space pictures. 



2 Berichte der deutschen chemischen Oesettschaft, Bd. 16, p. 2720. 



s Astaschewski : Zeitschrift fur physiologische Chemie, 1880, Bd. 4, p. 403 ; Irisawa, Ibid., 

 1893, Bd. 17, p. 351. 



4 Boehm : Pftilger's Archiv, 1880, Bd. 23, p. 44. 



5 Minkowski : Archiv fur exper. Pathologic und Pharmakologie, 1886, Bd. 21, p. 41. 



6 Festschrift zu R. Virchovfs 70. Geburtstag. 



7 Zeitechrift fur physiologische Chemie, 1894, Bd. 19, p. 426. 



*Loc. cit., and Archiv fur exper. Pathologic und Pharmakologie, 1893, Bd. 31, p. 214. 



