title: Emil Selenka on the embryonic membranes of the mouse and placentation in gibbons and orangutans.
abstract: BACKGROUND
  Emil Selenka made important contributions to embryology in marsupials, rodents and primates that deserve wider recognition. Here we review his work on early development of the mouse and placentation in the great apes.
  
  
  RESULTS
  Selenka was intrigued by germ layer theory, which led him to study inversion of the germ layers in the mouse and other rodents. He found it was growth of the ectoplacental cone that caused a downward shift in the position of the underlying ectoderm and endoderm, leading to an inside-outside inversion of these layers. In primates he made the important discovery that the embryos of gibbons and orangutans develop under a decidua capsularis. Thus all great apes, including humans, exhibit interstitial implantation; this is in contrast to other primates where implantation is superficial.
  
  
  CONCLUSIONS
  Selenka's work was thorough and brilliantly illustrated. It was an important influence on his contemporaries and was well known to scientists of the following generation. Embryologists continue to advance our knowledge of fetal membranes and placentation in the mouse, but Selenka's work on gibbons is unique and our knowledge of orangutan placentation is restricted to his specimens.
authors.affiliation: Department of Cardiovascular and Renal Research, University of Southern Denmark, DK-5000 Odense, Denmark. Electronic address: acarter@health.sdu.dk.
authors.forename: A M
authors.initials: AM
authors.lastname: Carter
authors.affiliation: Department of Development and Regeneration, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium.
authors.forename: R
authors.initials: R
authors.lastname: Pijnenborg
mesh_terms: D000818:Animals; D005321:Extraembryonic Membranes / Q000254:growth & development* / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D049672:History, 19th Century; D049673:History, 20th Century; D006801:Humans; D006922:Hylobates / Q000502:physiology*; D051379:Mice / Q000502:physiology; D010929:Placentation / Q000502:physiology*; D057079:Pongo / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal
keywords: Decidua capsularis; Germ layers; History of science; Interstitial implantation