I044 CARBOHYDRATE METABOLISM [pt. iii 



blastula and gastrula have any in them. At the neurula stage, how- 

 ever, while the first organs are being formed, glycogen appears again, 

 and rises in amount until it can be found in all the tissues all over 

 the body. In later periods all organs do not behave in the same 

 way, for in some of them the glycogen soon disappears again, while 

 in others it steadily accumulates during larval life. Thus in the 

 mesenchyme cells, the central nervous system and the eye-cups, its 

 appearance at the neurula stage is only transient, and there is none 

 there by the time that a length of 5 mm. is attained, but it persists 

 much longer in all the epithelial cells, and definitely increases in 

 amount in the skeletal and cardiac muscle. It will be observed that 

 these findings are roughly in accord with those of Claude Bernard. 

 Konopacki also studied the effect of the formation of the perivitelline 

 space on the glycogen in the frog's egg, and found that it corresponded 

 with a marked diminution of it — "le glycogene", he said, "disparait 

 presque entierement", but the contents of the perivitelHne space gave 

 a very strong reaction for glycogen, so that it would not appear to 

 be lost from the system as a whole. 



Thus the glycogen in the frog's egg at fertilisation found by Kolb; 

 Luchsinger; Athanasiu; Bleibtreu; and Kato (see Table 46 and 

 Appendix 11), is partly eliminated into the perivitelline space and 

 almost wholly used up by the cells of the embryo before gastrulation. 

 After that time more glycogen is formed and stored in the tissues, which 

 after a preHminary general distribution, hand over most of it to the 

 keeping of the liver and the muscles. The details were filled into this 

 bare outline by the long memoir of Konopacki & Konopacka. Thus 

 they showed that, after gastrulation, glycogen does not in general 

 appear in endodermal cells, e.g. liver and pancreas, though the gill 

 region is an exception. In the ectoderm it appears profusely, but does 

 not persist there except in the epidermis, where it exists even after 

 hatching. The organs of mesodermic origin take an intermediate 

 position, for after gastrulation, glycogen is found to a considerable 

 extent in them, but very soon disappears. The skeletal and cardiac 

 muscles form an exception to this rule. No glycogen seems to be 

 present at any time in the genital cells. During the hunger period 

 after the yolk-sac has been all used up, if no food is provided for the 

 larvae, glycogen disappears from all the places where it is stored. 

 Conversely, if food is given, the glycogen stores increase throughout, 

 and glycogen appears for the first time in the liver, the white matter 



