1020 CARBOHYDRATE METABOLISM [pt. m 



"avant que le foie foetal puisse executer ses fonctions, un veritable 

 organe hepatique placentaire qui produit la matiere glycogene." 

 Bernard was for long puzzled by the fact that he could demonstrate this 

 glycogenic function of the placenta with ease on guinea-pigs, rabbits, 

 etc., but not on ruminants such as cows and sheep, but he eventually 

 found that the reason for this was purely anatomical. In the case of 

 the ruminants, the vascular and glandular components are quite sepa- 

 rated, and, while the former continue to grow till term, the latter 

 disappear by an atrophic degeneration. At birth, then, there may 

 be very little left of the hepatically functioning part of the placenta. 

 "One must add", said Bernard, "that all the time the amniotic 

 placenta is increasing in size, the foetal liver possesses neither its 

 adult functions nor its adult structure, while precisely from the 

 moment that the foetal liver has attained an adult character and 

 that its cells having acquired their definitive form, begin to secrete 

 and store glycogen, the hepatic organ of the amnios begins to dis- 

 appear," Bernard reported also that the cells of the skin, the in- 

 testinal mucosa, the mucous membranes of the respiratory and 

 genito-urinary passages, the muscle-cells, etc., could be shown to 

 contain supplies of glycogen in foetal life, and at a time when the 

 liver was completely devoid of it. Glands and bony or nervous 

 structures, however, were always free from it. This led to a series 

 of researches on the glycogen content of tissues, mostly histochemical, 

 which will be referred to later. 



Immediately following Bernard's paper in the Annales des Sciences 

 Naturelles, there is to be found a note by Serres entitled "Des corps 

 glycogeniques dans la membrane ombilicale des oiseaux". Bernard's 

 communication, he said, revealed to him the nature of those little 

 glandular bodies which appear on the surface of the chick's blasto- 

 derm during incubation, and which he had figured previously with- 

 out knowing what they were. "We see these little objects", he said, 

 "from the twenty-fifth or thirtieth hour of incubation onwards. 

 Their whitish colour suffices to distinguish them from the blood 

 islands which have a reddish tint. At the thirty-fifth hour they 

 become of a clear yellow colour and their increased size allows 

 them to be more easily made out. . . . From the third to the sixth day 

 their volume continues to increase but the proliferating arteries and 

 veins partially hide them." About the 12th day they begin to dis- 

 appear, and from histological considerations this time corresponds 



