io6 RESPIRATION 



which accumulates in fatigued muscle. Lactic acid, either as 

 such or combined in the form of a salt, has been considered an 

 intermediate product in alcoholic fermentation, and Stoklasa 

 and Chokensky * state that they have isolated a zymase which 

 converts sugar into lactic acid accompanied by a lactacidase 

 which resolves the acid into alcohol and carbon dioxide. The 

 evidence, however, for lactic acid being an intermediate pro- 

 duct is inconclusive and in animal physiology the facts would 

 appear to warrant the statement that lactic acid has its origin, 

 at any rate in part, from protein. 



With regard to glucuronic acid, Spoehr has succeeded in 

 isolating it from certain Cactaceae, the only plants so far in 

 which it has been recorded. 



The depth of our ignorance of this important aspect of 

 respiration is obvious : and until all the possible successive 

 stages in the dissociation of fats, carbohydrates and proteins, 

 all of which are respirable, are known, it is impossible to trace 

 the sequence obtaining in the living organism. 



* Stoklasa and Chokensky : " Ber. deut. hot. Gesells.," 1907, 25, 122. 



