[022 



CARBOHYDRATE METABOLISM 



[PT. m 



These conclusions were criticised by Pfluger in 1903 with all his 

 usual vigour. He maintained that the histochemical reaction was 

 liable to be misleading, as in instances where it had been negative for 

 early embryos he had succeeded in isolating glycogen from them, and 

 even estimating it quantitatively. Pfluger did a good service in 

 drawing attention to the inadequacy of histochemical methods, and 

 soon a number of investigations appeared in which chemical analyses 

 were made. 



Barfurth himself, for instance, pubHshed figures for a rabbit embryo 

 liver and placenta, which are included in Fig. 278. Butte reported 

 a value of 8-7 gm. per cent, glyco- 

 gen for the embryonic liver of the 

 dog at term and of 0-42 for the ^ 

 corresponding maternal liver. 

 Paschutin found no glycogen in 

 the livers of cow embryos 10, 14 

 and 21 cm. long, but isolated a 

 certain amount from the liver of 

 an embryo 40 cm. long. At birth 

 McDonnell found 2 per cent. 

 Demant found as much as 1 1 -4 per 

 cent, in the liver of a dog at birth, 

 and noted that the quantity steadily decreased for several days after- 

 wards (see Fig. 277). The cat embryo at term, however, has not such 

 large amounts of glycogen in its liver, according to von Wittich, who 

 only found 0-23 per cent. It is difficult to assess these early papers. 



For the human embryo, von Wittich found 0-24 per cent, glycogen 

 at 5-5 months development. A. Cramer found an average of 1-45 per 

 cent, at term for liver glycogen, and o-o8 per cent, for placenta 

 glycogen. The latter figure was fixed at 0-52 by Moscati, who found 

 more in a placenta of the 7th month, and more recently at i-o6 per 

 cent, by Clogne, Welti & Pichon, though Bottazzi could hardly find 

 enough to estimate. Perhaps his placentas were not quite fresh, for 

 Moscati showed that on standing at room temperature their glycogen 

 content diminishes, and reaches nil 24 hours after the cutting of the um- 

 bilical cord. Adamov found i per cent, in human foetal livers. 



In 1907 Mendel & Leavenworth studied the occurrence of glycogen 

 in the embryo pig. Their results will be referred to again; here the 

 important point to note is that they could never find any in the 



Fig. 277. 



