258 SCIENCE PROGRESS 



it might arise entirely from the carbonates of the tissues and 

 tissue fluids of the animals, which were gradually decomposed 

 by the steadily accumulating lactic acid. This suggestion, so 

 far as it applies to frogs' muscles, is supported by Fletcher and 

 Brown's recent experiments ; but it is difficult to believe that 

 it holds for all other animals. For instance, Thunberg 1 showed 

 that the snail, Umax agrestis, and the mealworm, Tenebrio molitor, 

 when kept in nitrogen, gave out about 1,000 c.c. of C0 2 per 

 kilogram, or five times more C0 2 than the frog does under 

 similar conditions. Also I found 2 that if an excised mammalian 

 kidney were perfused with oxygenless saline it gave out about 

 ioo c.c. of C0 2 per kilogram. This C0 2 did not arise from the 

 carbonates of the tissues, as they had already been washed out 

 by a previous perfusion with oxygenated saline. Moreover, 

 the addition of lactic acid to such saline led to no increase of 

 C0 2 output. 



Part of the large volume of C0 2 evolved from the anaerobic 

 snails and worms is probably formed by glycolytic enzymes. 

 Thus Lesser 3 found that when earthworms were kept in 

 nitrogen they lost a large amount of their glycogen. In six 

 hours at room temperature from 5 to 37 per cent, of it dis- 

 appeared, and about half of it was shown definitely to be 

 converted into C0 2 and a fatty acid, probably valerianic acid. 

 Frogs kept in nitrogen lost on an average 17 per cent, of their 

 glycogen. A small portion of it was converted into glucose, 

 but what happened to the rest of it is unknown. Lesser thought 

 that it could not have been oxidised to C0 2 + H 2 by intra- 

 molecular oxygen, as he found that the heat produced by 

 anaerobic frogs, per unit of C0 2 evolved, was only a third as 

 great as that produced by frogs kept in air. Still this result 

 affords no evidence as to the origin of the C0 2 . Part of it was 

 doubtless expelled from the carbonates of the tissues by the 

 accumulating lactic acid, and with practically no production of 

 heat. The remainder may have been formed partly at the 

 expense of intramolecular oxygen or partly by glycolytic 

 enzymes. In any case it is evident that the evolution of C0 2 

 by animals kept under anaerobic conditions does not, by itself, 

 afford good evidence of the existence of zymase and other 



1 Thunberg, Skand. Arch. f. Physiol. 17, p. 133, 1905. 



3 Vernon, Jo urn. Physiol. 35, p. 53, 1906. 



3 Lesser. Zeit.f. Biol. 51, p. 287 ; 52, p. 282 ; 56, p. 467, I9 11 - 



