Discussion 117 



grown into it, then we found it could develop a certain degree of 

 independence and new cell formation. Although it did not grow to 

 full term it had, however, powers of intrinsic development without the 

 foetus. 



Hamilton: Whether or not the placenta persists will depend, I think, 

 on whether or not it has been vascularized, will it not? 



Amoroso: That is the point he means. 



Hamilton: It has not been vascularized in the early stages. 



Huggett: But if the mesodermal tissues, including vessels, grew within 

 the placenta, then it had power of development. 



Hamilton: Quite right. 



Villee: In humans, as you know, the occurrence of a hydatidiform mole 

 is a form of natural experiment of this type, for the foetus presumably 

 dies and only the placenta is left. We have studied several examples of 

 such moles and have shown that this tissue bears a strong resemblance to 

 normal placental tissue in its functional capacities. The little vesicles 

 which are present contain a fluid which is quite comparable to foetal 

 serum. The amino acids are concentrated in the vesicular fluid just as 

 they are in the foetal serum. The tissue itself has metabolic character- 

 istics when incubated in vitro which are like those of normal placenta. 



