146 Discussion 



radioactive glucose into glycogen, whereas at term this occurs at a rate 

 which is just barely detectable. I think this is primarily the result of a 

 decreased rate of synthesis rather than an increased rate of breakdown. 



Huggett: I was going to ask whether Prof. Jost could advise us whether 

 the foetal endocrines affect placental metabolism. Do you know 

 whether they actually act on the placental metabolism as apart from 

 the foetal organ metabolism? 



Jost: I know of no evidence in this field. It has been assumed that 

 the placental glycogen is necessary for the foetus until the time the liver 

 takes on the same function ; such an assumption might suggest that 

 there is some correlation between the changes occurring in the placenta 

 and in the liver of the foetus itself. Some results obtained on decapitated 

 rabbit foetuses do not support this idea since the placental glycogen 

 drops even when the liver does not store glycogen. But the foeto- 

 placental endocrine relationship needs further study. 



Dempsey: I want to comment on the reference point which Dr. Villee 

 used for the determinations he made. You refer your determinations 

 finally to the dry weight of the slice? 



Villee: Only for oxygen, as it is generally done that way. The rest of 

 the determinations are referred to the fresh weight of the tissue. 



Dempsey: In either case it is a reference to a weight determination. 

 But isn't there a considerable change in the solid components of the 

 placenta as it goes on to term ? My impression is that there is consider- 

 ably more collagen, for example, in the placenta at term than there would 

 be in some of the earlier placentas. 



Villee: The amount of solids goes from about 8 per cent up to about 

 13 per cent of the total weight. 



Dempsey: And some of that solid must be metabolically inert. 



Villee: Yes. 



Dempsey: So you have as your reference a shifting scale. Would it 

 be possible to have for reference some other determination, which is 

 correlated more sharply with the viable metabolically active tissue, with 

 the living cells, for example, nucleic acid, phosphorus, or something 

 of that sort ? Would you think that this would be as good or a worse 

 reference point than the weight? 



Villee: It would be at least as good, and perhaps better. Since these 

 changes are gradual and not particularly marked, I have plotted them 

 both as wet weight and as dry weight, and the changes are evident in 

 either case. 



Dempsey: Yes, but I was thinking that if there is an accumulation of 

 metabolically inert solid material during the course of pregnancy, then 

 the changes in the determinations which you observed would actually 

 be greater than your figures show, would they not ? 



Villee: That would be so if our slices were representative of the whole 

 placenta including the collagen. Of course, as collagen is a little diffi- 

 cult to slice we try to find a villus as free of this connective tissue as 

 possible. 



Dempsey: Even in the terminal villus, one of the very thin areas, 

 which I think Prof. Wislocki showed on the screen a little while ago, 



