106 THE CHEMISTRY OE THE TISSUES AND ORGANS. 
per cent, more of the total fat obtainable ; without such preliminary 
digestion, extraction with ether is useless for quantitative purposes. E. 
Bogdanow x believes that the fat which is thus soluble in ether with 
difficulty is a real constituent of the muscle plasma, and states that it is 
richer in volatile fatty acids than that from the surrounding connective 
tissues. For " Adipocere," see p. 20. 
Lactic acids. — Among the oxypropionic acids with the empirical 
formula C 3 H 6 3 , one called hydracrylic acid, or ethylene lactic acid, CtL 
(OH).CH 2 .COdH, is not found in the body. Small quantities of this 
material were formerly described 2 as occurring in muscle extracts, but 
this is not the case ; the acid mistaken for it was acetvl-lactie acid 
H 3 CH(aH 3 2 )COOH. 3 
The remaining lactic acids are stereochemical isomerides of 
ethylidene lactic acid. They are three in number, and differ in optical 
activity, and in the solubility, optical activity, and amount of crystallisa- 
tion water in their zinc, calcium, and lithium salts. 4 
Their formula is CH 3 .CH(OH).COOH. The differences between 
them are due, according to the theory of Bel and Van't Hoff, and as the 
expression stereochemical implies, to the space relationships of the atoms. 
The three isomerides are — 
(a) The optically inactive acid. This is the ordinary fermentation 
lactic acid, which occurs in milk when it turns sour ; it has been found 
in small quantities in muscle, 5 in the grey matter of the 1 train, and in 
some cases of diabetic urine. Its most characteristic salts are — 
Zinc lactate Zn(C 3 H 5 3 ) 2 + 3H. 2 ; soluble in fifty-three parts of water 
at 15° ; in six parts at 100° C. ; almost insoluble in alcohol. 
Calcium lactate, Ca(C 3 H 5 3 ) 2 + 5H 2 ; soluble in 9 - 5 of cold, and in 
all proportions in boiling water. Insoluble in cold alcohol. 
(b) Dextrorotatory lactic acid. — This is paralactic, or sarcolactic 
acid. This is the lactic acid par excellence of muscle. 7 It is found in 
the Wood, 8 particularly after muscular activity. 9 It is found in the 
urine after muscular activity, 10 during diminution of oxidation processes, 11 
in phosphorus poisoning, and after extirpation of the liver. 12 It is found 
as noted when we considered them, in many organs and tissues after 
death. Its best known salts are — 
Zinc sareolactate, Zn(C..H i O, ; ), + 2H.,0. Soluble in 17 5 parts of water at 
15° C.j and in 96 '4 parts of boiling 98 per cent, alcohol. 
I Arch.f. d. ges. Physiol., Bonn, Bd. lxv. S. 81. 
- Wislicenns, Ann, d. '.'hem. Leipzig. 1873, Bd. clxvii. S. 302. 
3 Siegfried, Ber. d. deutsch. diem. Gesellsch., Berlin, 1889, S. 2711. 
4 On lithium lactates, see Hoppe-Seyler and Araki, Ztschr. f. physiol. Ghent., Strassbnrg, 
1895, Bd. xx. S. 365. 
5 Heintz, Ann. d. Ohem., Leipzig, 1871, Bd. clvii. S. 314. 
,: Gschleidlen, Arch.f. d. ges. Physiol., Bonn, 1S73-4, Bd. viii. S. 71. 
7 Liebig, Ann. d. Chan., Leipzig. 1847, Bd. lxii. S. 326 ; Wislicenns, ibid., S. 302. 
8 Gaglio, Arch. f. Physiol., Leipzig, 1886, S. 400; Irisawa, Ztschr. f. physiol. Chem., 
Strassburg, Bd. xvii. S. 340. 
9 Spiro, Ztschr. f. physiol. Chem., Strassburg, 1877, Bd. i. S. Ill : v. Frey, Arch. f. 
I'll i.'-s/"/.. Leipzig. 1885, S. 5."' 7. 
10 Colasanti and Moscatelli, Jahresb. it. d, Fortschr. d. Thier-Chem., Wiesbaden, 1887, 
S. 212 ; Marcus, Arch.f. d. ges. Physiol., Bonn, 18S6, Bd. xxxix. S. 425. 
II Araki, Ztschr./. physiol. Chem., Strassburg, Bde. xv., xvi.. xvii., and xix. 
v - Minkowski, Ccntralbl. f. d. med. U'isscnsch., Berlin, 1885, No. 2: Arch.f. exper. Path, 
u. Pharmakol., Leipzig, 1SS6, Bd. xxi. S. 40 ; Maicuse, loc. cit.; Nebelthau, Ztschr. f. Biol., 
Munchen, 1889, Bd. xxv. S. 123. 
