UTKLUJS. '2*') I 



associated closely with that concerning the villus ectoderm and 

 syncytium, for the origin of the intervillous spaces is associated 

 naturally with that of the syncytium. According to one 

 theory, which seems to have the greatest number of supporters 

 (Virchow, Ercolani, Leopold, Waldeyer, Keibel, and others), 

 the intervillous spaces represent the widened capillaries from 

 the uterine mucosa, It must be remembered that at an early 

 stage the chorion and the decidua serotina lie with their sur- 

 faces closely applied to one another, and the epithelial layer of 

 the decidua is cemented to a similar layer of the chorion. In 

 this way villi grow into the decidual tissue, in which at the 

 same time the capillaries become dilated to a system of spaces. 

 These surround the villi, so that they become bathed in blood. 

 Also flat endothelial cells lining the intervillous spaces have 

 been observed by Turner, Leopold, Waldeyer, and Keibel, 

 which represent the lining cells of the capillaries. Injections 

 made by Waldeyer support this view. Many authors who 

 share this theory claim that the syncytium and the ectoderm 

 of the villus have different origins. The latter they describe 

 as foetal and the former as a part of the uterine epithelium. 



According to other authorities (v. Kolliker, Langhans, Hof- 

 meyer, Minot, and others), the intervillous spaces represent 

 the original spaces between the placenta foetalis and placenta 

 uterina. The two parts of the placenta are joined together 

 only by the villi. According to this theory, the intervillous 

 spaces are interplacental cavities which originally contained no 

 blood and became filled only when the maternal vessels opened 

 into them. Almost all the adherents to this theory claim that 

 both layers of cells covering the villi are t)f foetal origin, and 

 according to Minot's theory the syncytium is a differentiated 

 product of the ectoderm layer beneath. 



The maternal part, or placenta uterina, represents the decidua 

 basalis, which has certain characteristics that distinguish it from 

 other deciduaB. From the fifth month on, there develop in it 

 large cells (giant cells) containing many nuclei. These cells 

 are present in large numbers in the ripe placenta. From the 

 side toward the placenta foetalis more or less thick connective- 



