208 Discussion 



Black : On the genetic side it is very odd that one gets this scatter right 

 along the Une. One would think that, according to Mendel, one would get 

 segregation at the two ends of the line. 



I was not clear whether there was an excess of fluid in the red cells. 

 In other words, in the foetal sheep or man was there an excess of 

 potassium per litre of red cells? Was there any difference in phosphate 

 content? Differences in phosphate content have been described, I 

 think, by Prankerd (1955, Clin. Sci., 14, 381) and others in connexion 

 with the sickle cell problem, and I wondered whether that side had 

 been gone into with foetal versus grown-up sheep. 



Karvonen: I am afraid I gave a wrong impression when I said the 

 scatter was all along that line. There is a very clear concentration at 

 each end of the line but there is also a group in between. Within each 

 group, however, there is quite a considerable scatter which is due to a 

 permanent, individual characteristic of each sheep. The statisticians say 

 that there is quite a high intra-individual correlation. 



The foetal cells contain more water than the adult cells. In sheep I 

 do not think that any determinations of the phosphate have been done, 

 but in man and in pig it has been found (McCance and Widdowson, 

 1956) that the phosphate of the foetal cells is higher. 



Davson : It must be realized that when red blood cells are analysed, 

 very large numbers are used; there may well be differences in concen- 

 trations of potassium and sodium amongst the individual ones, and they 

 could well fall into groups which would never be discovered. Variations 

 in the Na/K ratio could be reflections of variations in the proportions of 

 high potassium and low potassium cells, which would give a continuous 

 scatter right along the line. 



