Chronological Changes in Placental Function 119 



£ 90- 



Ul 



o 



5 80 



E 



% 70 



ANIMAL MGS N4 TRANSFERRED TOTAL GESTATION " 

 PER GM PLACENTA PER HR. PERIOD IN DAYS 



AT MAXIMUM 



GUINEA PIG 6.26 67 



1 0.4- 23 



9.25 32 



0.79 62 



0.43 154 



0.028 114 



RAT 



RABPiT 



CAT 



GOAT 



SOW 



04 05 06 07 



PERIOD OF GESTATION IN TENTHS OF TOTAL 



Fig. 1. Transfer of sodium across unit weight of placenta in unit 

 time in different species. (After Gellhorn and Flexner, 1942.) 



rats an amount of 59 Fe adequate to produce a constant specific 

 activity in the mother which may possibly also have been the 

 maximum saturation. There was a rise in the total iron in 

 the litters and an increasing percentage of labelled Fe was 

 recovered from the litters (Fig. 2). But when the iron/foetal 

 26 r 



14 



Injection Fe 59 Da y s 



Fig. 2. Percentage of labelled iron recovered from litters at varying ages and 

 the number of rats in the litter. Continuous lines indicate upper and lower 

 limits, and broken line the approximate mean recovery curve. Weaning at 

 21-28 days after birth. (Huggett and Widdas, 1949.) 



