SECT. 8] CARBOHYDRATE METABOLISM 1021 



with the arrival of the foetal liver cells at a stage suitable for the 

 storage of glycogen. "May we not say", continued Serres, "that there 

 exists in the case of the chick a diffused hepatic organ, or a transitory 

 liver, analogous to that which M. Claude Bernard has just demon- 

 strated in the placenta of ruminants ? " 



The work of Claude Bernard was for many years afterwards 

 repeated and confirmed in a fragmentary manner. For the most part 

 the work was histochemical, depending entirely on the iodine method. 

 Thus Godet in 1877 described a "glycogen layer" in the rabbit's 

 placenta. Langhans found none in the fully developed human 

 placenta, though it was plentiful at eadier stages, as Merttens showed. 

 Maximov, who made a very detailed study of the rabbit placenta, 

 described the glycogen as increasing in amount up to a certain 

 point, and then dying away. This was also observed by Ulesko- 

 Stroganova and by Chipman. who, however, differed greatly between 

 themselves as to the actual situation of the glycogen. Chipman 

 never found glycogen in the foetal part of the rabbit placenta. It 

 appeared in the maternal part first on the 8th day, and increased 

 rapidly in amount, reaching a maximum between the 12 th and i6th 

 days. After that time it diminished steadily, and after the 22nd day 

 there were only found small glycogen granules scattered in the midst 

 of conglomerate masses of uni- and multinuclear cells, save in the 

 zone of separation, where some cells remained distinct and retained 

 their granules of glycogen. Glycogen was not found by Chipman 

 in the foetal Hver of the rabbit before the 22nd day, after which it 

 increased rapidly and steadily till birth. He did not observe any 

 diminution after birth. Other histochemical workers were Rouget; 

 Marchand; Brindeau; and Schonfeld, who all reported first an in- 

 crease and then a decrease in the glycogen of the rabbit placenta. 

 Jenkinson; Gierke; and Saake worked on the mouse placenta, and 

 published similar results. Driessen and Barfurth investigated that of 

 the guinea-pig, Kajimura that of the bat, and Happe; Plesch; and 

 Todyo that of man, from this point of view. A particularly interest- 

 ing result was that of Kiilz, who confirmed Bernard's finding that 

 glycogen was present in the 2-day-old chick embryo, but could not 

 confirm the presence of glycogen in the cicatricula. The histochemical 

 workers did not confine their attention to the placenta, and several 

 of them, especially Barfurth, stated that in the early stages of develop- 

 ment little or no glycogen was to be found in the foetal liver. 



