FCETAL NUTRITION: THE PLACENTA 477 



coagulation necrosis or symplasma, as shown by the " Fibrin- 

 streifen," which are comparable to the fibrinous deposits in the 

 rabbit's placenta. The layers of fibrin in the serotina were first 

 described by Nitabuch. 1 They may be seen as early as the 

 sixth week, and even earlier in the reflexa (Webster). They 

 gradually extend more deeply into the substance of the decidua, 

 and also occur in the vessel walls. They are, however, most 

 marked on the surface, at or near the junction of the maternal 

 and foetal tissues. That they are due to the influence of the 

 ovum is highly probable from their absence in the vera. Whether 

 the symplasma is formed from the blood or the decidua, or both, 

 is not known. It is probably absorbed by the villous ectoderm 

 during the greater part of pregnancy. 



According to Webster, there may be a new formation of de- 

 cidual tissue during pregnancy, from irregularly distributed 

 groups of active cells which are present at all periods in the 

 maternal part of the placenta (see p. 368). 



The uterine glands take no part in the formation of the 

 placenta. By the sixth week their superficial parts are largely 

 obliterated, and the deeper parts degenerated. At a later stage, 

 only a few blind ends are seen next the muscular layer. Though 

 their epithelium offers a considerable degree of resistance, and 

 is visible for a long time, its secretory power is probably lost very 

 early. According to Gottschalk, 2 the glandular epithelium 

 undergoes a fatty degeneration, but Bonnet 3 states that the 

 change is a hyaline one. In the vera the glands increase in size 

 and secrete actively for a time. Their secretion is found as a 

 milky fluid in the uterine cavity. 



Glycogen. Glycogen is present in the early stages of preg- 

 nancy. Langhans 4 demonstrated it in the decidual cells, in the 

 cellular proliferations of the trophoblast at the tips of the villi, 

 and in the mesoblast. It was absent in the canalised fibrin and 



1 Nitabuch, " Beitriige zur Kenntnis der menschlichen Placenta," Inaug.- 

 Dissert., Bonn, 1887. 



2 Gottschalk, " Weitere Studien viber die Entwickluug der menschlichen 

 Placenta," Arch. f. Gynak., vol. xl., 1891. 



3 Bonnet, "Ueber Syncytien," &c. , Monateschr. f. Oeburtsh. u. Oyniik., 

 vol. xviii., 1903. 



4 Langhans, " Ueber Glykogen in pathologischen Neubildungen und den 

 menschlichen Eihiiuten," Virchow's Arch., vol. cxx., 1890. 



