CHEMICAL BASIS OF THE ANIMAL BODY. 129 



times, notwithstanding the evidence of the production of large 

 amounts of sarcolactic acid during muscular contraction (see 

 above), the view has been put forward that the acid reaction of 

 contraction is due rather to other substances, as for instance acid 

 phosphates, than to the acid. 1 This view is by no means proved 

 ami is incompatible with the preponderating evidence of the re- 

 searches already quoted on the relationships of this acid to mus- 

 cular activity, and of more recent observations. 2 It is possible 

 that the acid reaction of active muscle is of complex origin, being 

 partly due to lactic acid, which by acting on an alkaline phos- 

 phate may convert it into an acid salt, while finally there is an 

 excess of the lactic acid, most marked in rigor. 



There is but little doubt that the glycogen normally present in 

 muscles is diminished in amount during their contracting activity. 

 and it has been frequently urged that the acid reaction of muscle 

 is due to the formation of sarcolactic acid from this glycogen. 

 This view seems to rest entirely on the fact that during activity 

 glycogen disappears and lactic acid is formed, but is devoid of 

 convincing experimental evidence. It is known that a muscle 

 free from all glycogen can become acid during activity, and bear- 

 ing in mind that the acidity of active muscle is proportional to its 

 power of doing work, and to the work it is called upon to do, 3 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. 4 

 Glycogen is according to this view to be regarded rather as a con- 

 venient 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 a (OH) . CH, . COOH. 



This acid has been usually described as accompanying sarcolac- 

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

 taking advantage of the varying solubilities of the zinc salts of 

 tin- two acids. 6 



More recent researches have however made it probable that 

 what has usually been described as ethylene-lactic acid, obtain- 

 able from muscle-extract, is really acetyl-lactic acid, CH, . CH 

 (C,H 8 O a ) COOH, the true ethylene-lactic acid being hydracrylic 

 acid, which does not occur in the animal body. 6 



Aatawhewsky. 7*. f. phytlol. Chem. Bd. iv. (1880), S. 397. Weyl u. Zi-itl-r, 

 /'i'l. IM vi. (is- 



WfTtt.or. IMhiirrr's .In/,. IM. xi.vi. (1890), S. 63. Cf. Warren, Pflugers Arch. 

 Bd. xxiv. (isxi). S .391. it L i 



' H-i.l.-nli:iin. M.. Imninrhr f^ixtunij Wiinnmit.nrk. . ,SV..//m.svi/.- bei der Muikcl- 

 th;n;,,l.;ii. I^ij,/;.;. HC,4. K:mk-. 1\ MUMS. Leipzig. 1865. Hermann, Untert. rf.rf. 



tfir, ,/,>.-',/. M,,J;,!n. Berlin. 1 -'',: 



Cf UVrflirr /"-. Of I .llihurt. ...//. PhyM, Vol. VIM. (1887), p. 154. 



Wislicfuus. Ann <t. f'h.m. . /Vii-i. IM. 01 NX n M7:). s - ; 



Siegfried, Ber. d. d. chem. Gesell. Jahrg. 1889, S. 2711. 



9 



