I054 CARBOHYDRATE METABOLISM [pt. iii 



respect to lactic acid. Yoshikawa in 191 3 found 3 mgm. per cent, 

 in the white and 1 2 mgm. per cent, in the yolk of the fresh egg of 

 the marine turtle Thalassochelys corticata, and the subject was later pur- 

 sued by Sendju. It turned out that just as Tomita had found a peak 

 of lactic acid in the development of the bird so Sendju found one 

 in that of the chelonian reptile. Beginning at 8 mgm. per cent, in 

 the fresh egg, the lactic acid rose to 41 per cent, on the 15th day, 

 falling to 1 5 per cent, on the 45th day. A high value for the newly 

 hatched tortoises may perhaps have been due to the muscular effort 

 involved. The general trend of the figures affords another indication 

 of the similarity between the general metabolic picture of the various 

 sauropsida in pre-natal life. 



8-14. Fructose 



Attention must finally be given to the fructose question which is 

 the most enigmatic aspect of embryonic carbohydrate metabolism. 

 It begins with Claude Bernard, who in 1855 noted that the sugar 

 of the human amniotic liquid was laevorotatory, but that this con- 

 dition was no longer present at term. In 1904 Giirber & Grunbaum 

 observed that 40 per cent, of the reducing carbohydrate of the amniotic 

 and allantoic fluids of the horse and pig was fructose. This was con- 

 firmed and much extended by the classical researches of Paton, Watson 

 & Kerr in 1907, who reported the presence of fructose in the amniotic 

 and allantoic fluids of the sheep, cow, and probably the dog. The blood 

 of the sheep embryo contained in one experiment 420 mgm. per cent, 

 of fructose, but it was not demonstrable in the liver. Then in 1922 

 Takata found that fructose was the only carbohydrate present in the 

 amniotic fluid of the whale Balanoptera, and not long afterwards Orr 

 noted that human and goat foetal blood give the Selivanov reaction, 

 and have an abnormally low rotation. In human foetal blood the 

 fructose/glucose ratio seems to be 1/2 and the former sugar does not 

 completely disappear at birth. There may also be a fructosuria of 

 pregnancy (van Creveld & Ladenius). Are the rare cases of fructo- 

 suria in adults cases of arrested development, just as icterus neo- 

 natorum seems to be a continuation of a normal pre-natal condition? 



