46o THE PHYSIOLOGY OF REPRODUCTION 



this situation till the greatei: part of the fat has disappeared from 

 the placenta. It is either transmitted to the foetus in a form 

 which does not reduce osmic acid, or formed in the foetus itself 

 from other substances. At birth the foetal viscera, especially the 

 liver, have a considerable store of fat vs^hich increases during suckling. 



Glycogen Metabolism 



The presence of glycogen in the placenta of the rabbit was 

 discovered by Claude Bernard '^ in 1859. He showed its increase 

 and subsequent decrease during pregnancy, and concluded from his 

 observations that the placenta carried out for the foetus, in the 

 first half of iritra-uterine life, the glycogenic function subsequently 

 assumed by the foetal liver. Godet ^ described two areas of glycogen- 

 containing cells, one immediately underlying the foetal villi, the 

 other in the deeper part of the placenta. Maximow investigated 

 these cells at different stages of pregnancy; he found glycogen in 

 the decidual cells of the vascular sheaths at the eighth day, gradually 

 increasing in amount and playing an important part in the nourish- 

 ment of the trophoblast. In the later stages glycogen disappeared 

 and the decidual tissue was transformed into polygonal multinucleate 

 cells rich in fat. Chipman recorded detailed observations in a more 

 complete age-series from the eighth day to the end of gestation. He 

 showed that glycogen was always present in the maternal part of 

 the placenta, but never in the foetal. Occurring in the decidual cells 

 of both zones, it increased and reached a maximum between the 

 twelfth and sixteenth days ^ (Fig. 131) ; then it steadily diminished, 

 and in the last week only a few granules were found scattered in the 

 conglomerate masses of decidual cells. At the zone of separation, 

 however, glycogen granules were stiil contained in decidual cells. 

 Chipman also examined the foetal liver. In it he found that glycogen 

 appeared at the twenty-second day, and increased rapidly and 

 steadily in amount till the end of pregnancy. 



These results have for the most part been corroborated by 

 chemical analyses carried out by the writer, working in collaboration 

 with Dr. W. Cramer.* They determined quantitatively the glycogen 

 of the maternal placenta, foetal liver, and remainder of the fcetal 



1 Bernard, "Sur une nouvelle fonction du placenta," Comp. Rend. Acad. Soi.,- 

 Paris, 1859. 



2 Godet, " Eecherches sur la structure intime du placenta du lapin," Dissert. 

 Inaug. a la Fac. de Med. de Berne, Neuveville, 1877. 



^ It has been shown that the corpus luteum in the rabbit reaches its maximum 

 about the same time. (See Hammond and Marshall, Proc. Boy. Soc, B., vol. 

 Ixxxvi}., 1914 ; and Hammond,, Prac. Roy. Sac, B., vol. Ixxxix., 1917.) 



* iiochhead and Cramer, " The Glycogenic Changes in the Placenta and the 

 Foetus of the Pregnant Babbit," Proc. Roy. Sac. London, B., vol. Ixxx., 1908. 



