160 Discussion 



Strauss: I wonder if Prof. Harrison found any potassium in the walls 

 of the foetal blood vessel of the placenta. A couple of years ago we 

 found some potassium in human mature placentas. The potassium is in 

 the syncytiotrophoblast as well as in the walls of the foetal blood vessels. 

 We found about the same distribution of the calcium. Have you any 

 experience of that ? 



Harrison: We have not done any quantitative estimations on that. 

 We have only made some autoradiographs, and one can detect the 

 potassium in the chorion, but we have not looked carefully or made any 

 comparison with the amount in the walls of the blood vessels. We have 

 estimated the uptake in the umbilical cord and that is insignificant 

 compared with the uptake by the placentome. So it was from that 

 experiment that we thought we could argue that the connective tissue 

 in the placenta did not take up potassium to a degree parallel to the 

 chorionic epithelium. 



Huggett: You are not distinguishing between Wharton's jelly and the 

 vessels of the cord ? 



Harrison: We simply took a chunk of the cord. 



Hamilton: How early do the haemorrhages occur, Prof. Harrison? 

 I have not seen those before in any of the ungulates. 



Harrison: That picture I showed was, I am almost sure, 41 or 42 days 

 old, but we found such localized haemorrhages right from the start of 

 the formation of the placentomes. It is quite different from the state of 

 affairs that we found in the deer. We did not find any haemorrhages, 

 as far as I can remember, at any stage in any species of deer we looked at. 



Hamilton: I take it that the trophoblast is eroding maternal blood 

 vessels in some way or another. 



Amoroso: I have no doubt in my own mind that the trophoblast is 

 endowed with erosive properties. That it may destroy the maternal 

 capillary endothelium is a real possibility. As to the question of the 

 two types of placentomes to which Prof. Harrison has drawn our atten- 

 tion, these have been figured in the uterus of the sheep by Cloette and 

 they are also known to occur in the uterus of many antelopes. They are 

 not indicative of age changes in the placenta. 



Huggett: It was in the goat that I first saw it. 



Amoroso : On the other hand, changes in the connective tissues which 

 may often be very widespread, are invariably associated with placental 

 degradation. 



Montagna: A great deal has been said about the efficiency of the 

 placenta and I believe that we are being as arbitrary with this term, as 

 we have been also with ageing and senescence. I wonder who is the 

 better judge of efficiency, our arbitrary determination of efficiency, that 

 is, whether or not potassium or iron, etc., go through at a certain rate 

 that we decide is efficient or not inefficient, or if the embryo is a better 

 judge of efficiency. 



Amoroso: Are you suggesting that it is the quality of the embryo at 

 the end of gestation which is the criterion? 



Montagna: I am saying that the placenta is always efficient if the 

 embryo is going to survive. 



