TIII: i (] i .\ i. MIVI CAMS >r M \ \i M \ 



yolk -ac and allantoj>. KT6 also drawn out in tin- into 



two long tapering mils. 



On tin- entire rarfB06 "f the choi-ion. \\ith the exception of the 

 two ri,d> nt the sac, there have ari>en rows of very \a~-ular pads, 

 which radiate from separate smooth round >p<>t- of the membrane. 



and are covered at their ed^-> with small simple papilla-. 



macoos membrane of the uterus is exactly littel int.. the elevation- 

 ami depressions of the chorion. There are also found on it circular 

 smooth ]i laces similar to those of the oho:'ion. which are further 

 noteworthy from the fact that it is only on them that the tubular 

 uterine glands open out. At birth the interlocking .-urfacas of 

 contact separate from each other without any loss of substance on 

 i he part of the mucous membrane of the uterus; for the pads and 

 small papilla- are easily withdrawn from the depressions which B6TV6 

 for their reception. 



In the third group a special or^raii, the placenta, or afterbirth, 

 has been developed for the purpose of intra-uterine nutrition. Its 

 origin was brought about by separate portions of the chorion having 

 assumed different characters, owing to the unequal >i/.- and distri- 

 bution of the villi. 



One part exhibits a condition in which the villi are entirely gone 

 or much stunted, so that the surface of the membrane feels smooth ; 

 moreover, it possesses few blood-vessels or is ent irely destitute of them. 



Another part of the chorion contains, closely packed together, villi 

 which are extremely long and covered with many ramifying lateral 

 branches ; furthermore, it receives large blood-vessels, which approach 

 the tufts of villi and distribute their terminal capillaries to the finest 

 lateral ramifications of the latter; finally, it has entered into the 

 most intimate relations with the mucous membrane of the uterus. 

 Wherever the latter comes in contact with the tufts of villi it 

 is much thickened, very vascular, and in a state of active growth. 

 It encloses numerous branched cavities of varying size, into which 

 the villi of the chorion exactly fit. 



The entire structure is called a placenta, in which ths prirt of the 

 chnri<>n tr/iic/i is cnrnvd with rilli is lUatinijiiixhed as th> 



iit. mid the part of the mucov^ membrane of t/c' ////;/* >r/' 



trit/> d/iff m/iifited to the latter as the j -a. Both 



parts together constitute an onran for the nutrition of the embryo. 



The term pl.u enta has often been extended to the kind of chorion 

 which is evenly covered with small villi, nidi as exists in the 

 \ etc., and the designation of diffuse placenta has been cr- 



