The second Bo j anus correctly considered inaccurate 

 because the embryonic organs of man and horses have different 

 structure. In order to explain, Bojanus gaye the following 

 description of the topography of the fetal membranes and 

 embryonic organs of horses. The fetus is covered with the 

 amnion, which with the umbilical vessels goes out from the 

 allantoic duct and widens, forming the voluminous allantoic- 

 sac. This sac bends around the amnion and lines the entire 

 chorion, with the exception of that place where the blood 

 vessels go out. "Therefore," Bojanus said "the amnion and its 

 fetus lie in the allantois exactly as the intestines in the 

 peritoneum." This accurate comparison shows that the 

 intestines lie not in the cavity of the peritoneal sac, 

 but outside it and are covered with folds of the peritoneum. 

 Bojanus concluded with the following words: "The amniotic 

 sac does not swim in the allantoic fluid entirely; the allantois 

 and the amnion forms an independent closed sac, located between 

 the amnion and chorion and next to the external wall of the 

 amnion and the internal wall of the chorion." This, according 

 to Bojanus, is characteristic for the fetus of the horse as 

 well as for other mammals — dogs, cats, and ruminants. 



In another place (ISIS, 1817, p. 877), Bojanus entered 

 into controversy with Emmert. Emmert stated that the duct of 

 the umbilical sac Cyolk duct) is formed apparently only at the 

 end of development, being formerly unconnected with the cavity 

 of the intestinal canal. Bojanus referred to his data, and 

 to what "Wolff had forty years earlier already showed to the 

 contrary, so obviously that the subject could be considered 

 completed." 



In sheep embryos Bojanus found basically the same 

 situation as in the embryos of dogs and horses. In an article 

 about the embryonic membrane and organs of sheep, Bojanus 

 determined that the allantoic duct entered into the posterior 

 end of the peritoneal cavity. Near the duct, both the umbilical 

 arteries and the umbilical veins extended into the peritoneal 

 cavity, divided, and turned toward the liver. The stem of the 

 umbilical sac in the embryonic body was directed straight 

 toward the intestinal canal. 



In 1820 Bojanus again returned to the embryology of dogs 

 and gave an anatomical description of a twenty-four-day-old 



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