450 OUTLINES OF CHORD ATE DEVELOPMENT 



sinus. This is incompletely separated from the remainder of 

 the cavity by an irregular septum known as the closing plate. 



At parturition, when the amnion has been ruptured and the 

 amnionic fluid and foetus have been expelled by the contrac- 

 tions of the uterine musculature, the amnion itself and the 

 placenta and deciduse come away later. The decidua basalis 

 separates first through the spongy region, just outside the 

 glandular layer (Fig. 185, Tr-Tr). The decidua vera similarly 

 is divided through the remains of its spongy layer and comes 

 away with the placenta. The so-called " after- birth " therefore 

 includes amnion, chorion, decidua vera, placenta, and a por- 

 tion of the decidua basalis. The hemorrhage which follows this 

 separation of the maternal tissues is diminished by the general 

 contraction of the uterine walls. The entire uterine cavity is 

 then lined with the deeper decidual layer containing vestiges 

 of uterine glands, and from this tissue the decidua is formed 

 anew. 



REFERENCES TO LITERATURE 



CHAPTER VI 



This list contains but a very few of the important works bearing 

 directly upon the topics of the chapter. For very full references to the 

 literature of Mammalian development see especially the works in the 

 following list, by 0. Hertwig, Handbuch, etc., 0. Hertwig, Lehrbuch, 

 etc., F. Keibel and F. P. Mall, Handbuch, etc., Hubrecht, Marshall, and 

 Minot, 1893. 



ASSHETON, R., A Re-investigation into the Early Stages of the Develop- 

 ment of the Rabbit. Q. J. M. S. 37. 1894. On the Causes 

 which lead to the Attachment of the Mammalian Embryo to the 

 Walls of the Uterus. Q. J. M. S. 37. 1894. The Primitive 

 Streak of the Rabbit; the Causes which may determine its Shape, 

 and the Part of the Embryo formed by its Activity. Q. J. M. S. 37. 

 1894. The Morphology of the Ungulate Placenta. Phil. Trans. 

 Roy. Soc. 198. 1906. The Segmentation of the Ovum of the 

 Sheep, with Observations on the Hypothesis of a Hypoblastic 

 Origin for the Trophoblast. Q. J. M. S. 41. 1898. The 

 Development of the Pig during the First Ten Days. Q. J. M. S. 41. 

 1898. Early Ontogenetic Phenomena in Mammals. Q. J. M. S. 

 64. 1909. 



