[052 



CARBOHYDRATE METABOLISM 



[PT. Ill 



acid — this would lead to a temporary accumulation of the inter- 

 mediate product.^ Unfortunately we do not yet know the real meaning 

 of this accumulation. In order to penetrate a little farther into the 

 working of these processes, Tomita injected both glucose and alanine 

 into the hen's egg at the beginning of development. He found that 

 the addition of glucose to the egg in this artificial way led to a 50-70 

 per cent, increase of lactic acid in the white, and to a definite increase 

 in the yolk, though not to more than 15 per cent., and that in only 

 one case. This apparent isolation of the yolk from the events going on 

 in the white during the first week of incubation has been noticed 

 before when we were considering the effect of injections of glucose on 

 the free glucose of the yolk and ^ .^ 



white. It was interesting that 

 the addition of 200 mgm. of 

 glucose had no more eflfect in 

 increasing the lactic acid pro- 

 duction than the addition of 

 50 mgm., from which it may be 

 inferred that the relationships 

 considered cannot be simply 

 governed by mass action (see 

 Fig. 293). The lactic acid pro- 

 duced amounts at its maximum 

 to about 46 mgm. per egg, and 



CO ''° 



060 



I 50 



130 

 °'20 



Fig. 293. 



the amount of free glucose lost during the first 5 days is approximately 

 55 mgm. (see Fig. 267). When it is remembered that the estimate of 

 the carbohydrate combusted by the 5th day is something very close to 

 10 mgm., the correspondence is remarkable, and leads to the inference 

 that what is not burned can almost entirely be accounted for as lactic 

 acid. After that we lose sight of it. The decrease in free glucose is more 

 marked in the white than in the yolk (see Fig. 268), but the increase in 

 lactic acid is more marked in the yolk than in the white. Comparative 

 estimations of the lactic acid content of the white yolk and the yellow 

 yolk would be of great interest. 



^ It is interesting in this connection that Neuberg, Kobel & Laser have shown the 

 mechanism of lactic acid production in the chick embryo to be identical with that in 

 other tissues. Acetone powders of 8-day embryos give with hexosephosphate good yields 

 of methylglyoxal, showing the presence of active glycolase. The co-enzyme (co-zymase), 

 which assists the ketonaldehydemutase in transforming methylglyoxal into lactic acid, has 

 also been shown to exist abundantly in the embryo rat (Sym, Nilsson & v. Euler), mouse 

 (Waterman), and pig (Kraut & Bumm). 



