Tin: FU:T\I. MI MCI; VNES >! M \\. 



249 



part, which has IM-COUP- OVergrOWD by tin- decidua ivllcxa (fig. 143). 

 While <ii tin- latter tin- \illi <:') -as- i.. u the former th<y 



merease enormously in si/e ami tab- tin- form <>f lonir, ami af the 



ha-e thick, treeliko, branching .structures ( :). which, unit-d int., 

 tufts, project 

 far beyond (In- 

 Mil-fact- of the 



membranothst 



lu-Ml'v til. Ill, 



and L r ro\v into 

 ]>its of the ma 

 ternal mucous 

 membrane (ds). 

 This part, to 

 which wr shall 

 .u'ivt' more par- 

 ticular atti-ii- 

 tion at the 

 time of inves- 

 tiirating th<> 

 mature }>la 

 centa, is tln-rf- 

 fore distin- 

 guished as 

 chorion fron- 

 dosum from the remaining larircr part, tlie chorion lave or tin- 



Fig. 143.- Diagrammatic section through the gravid human uterus with 



contained embryo, after LM;I r. fi-.-n, 15 M ; 

 al, Stalk of tlie ;illaiit"is ; n>>. nnil>ili<.-.il vesicle; am, amnion ; *h 



chorion; dt, decidua serotina; du, decid\i;i vcni ; dr, decidu:i 



reflexa; I, Fallopian tube; c, cervix uteri ; u, uterus ; ;, villi of 



ili.' f.rta! iilao-nta : .'. \ illi ( tin- i-hi>ri>ui laeve. 



The expression " smooth chorion " is, .strictly speaking, not quite 

 applicable. Of the villi which are at fir>t everywhere developed, 

 some afterwards remain preserved on the chorion heve, especially in 

 the vicinity of the placenta. They grow into the decidua rellevi. 

 etlecting a lirm union with it (fiir. 143 z'). 



At the same time a second distinction between chorion frondoMim 

 and chorion heve is developing. In the territory of the latter 

 blood -ve.-v-eK arising from the umbilical M to dwindle, 



whereas the former becomes more and more abundantly supplied 

 with blood-vessels, and finally alone ivc-i\e> the terminal distribution 

 of the umbilical arteiies. Thus the one region becomes destitute of 

 Is. \\hile the other becomes extraordinarily vascular, and the 

 nutritive or^an for the embi 



lli.Moloirically the chorion l;e\e. which upon examination from the 



