47^ THE PHYSIOLOGY OF REPRODUCTION 



tions have lieen made regarding the metaliolism of iron-einitaiuing 

 .siilistances. 



Guinea-Piy. — In the guinea-pig tlie ovum is agaiji completely' 

 surrounded l>y decidua. Reichert ^ was the first to notice that the 

 ovum lay in a special cavity, "a little nest." ISischoff- stated that 

 the nest \vas only temporary, and the ovum again appeared in the 

 uterine cavity, only that part of the nest remaining which formed 

 the ]ilacenta. After a long interval this was proved to be wiong liy 

 Reichert'' and Hensen."' 



The fertilised ovum reaches the uteius as a moiula (ir early Ijlasti i- 

 cyst, surrounded by the zona radiata. On the seventh day the zona 



mes 





Aly*-' 



Fig. 1.34. — Longitudinal section of the uteius and implantation cavity of the 

 guinea-pig. (From Duval's " Le Placenta des Eongeujs," Jonm. dr PA'/Kit. 

 >'t <h III Mijs., 1892.) 



ines, Mesometrial border ; c/l, utei'ine glands ; /, uteiine linnen : 

 h/j blastodermic vesicle. 



disappears and emliedding begins, but e^'en Ijefoie this, according to 

 von Spee,^ the ovum is fixed l.iy processes which extend from the cells 

 (if the implantation pole through the zona and c(.ime intd direct 

 metabolic relationship with the epithelial cells. As in the nmuse, 

 the blastocyst remains small, about one-tenth of a millimetre in 

 diameter. At its point of Cdntact with the mucosa, the epithelium is 

 rapidly eroded, and absorljed along with its fat globules by the fVrtal 

 ectoderm. At the same time changes occur in the deeper layers. In 



^ Reichert, " Ueber die Bildung der hinfalligen Haute der Uebarmuttei,' 

 MkUer'x Ardi., 1848. 



'' Bischoff, Eiitifickhniy ilea MeiTschu'einrheiis, 1852. 



•' Reicheit, "Beitrage zur Entwicklungsgeschichte des Meeischweincheiis," 

 Ahhandl. d. AJcad. d. Wisseiisch. zu- Berlin, 1861. 



* Hen.sen, " Beobachtungen iiber die Befruchtung und Entwicklung des 

 Kaninchens und Meerschweinchens," Zeit. f. Anat. u. Entuni-k., vol. i., 18r56. 



" Von Spee, " Die Implantation des Meerschweincheneies in die Uterus- 

 wand," Zeit. f. Morplwl. u. Anthrnpol., vol. iii., 1901. 



