Biochemical Evidence of Ageing in the Placenta 131 



and decidual surfaces of the placenta and that slices cleaned 

 of blood by exhaustive washing with cold saline and those 

 cleaned by blotting on filter paper showed similar rates of 

 metabolism. Slices prepared from placentas which had been 

 standing 60 minutes at room temperature showed metabolic 

 rates 20 per cent less than those cut immediately. 



Oxygen Consumption 



A gradual decrease in the rate of oxygen consumption of the 

 placenta as gestation proceeds has been reported previously 

 (loc. cit.). The present series includes thirty term placentas 



2 - 



.!••■ 



10 



15 



20 



25 



50 



55 



40 



WEEKS OF PREGNANCY 



Fig. 1. The oxygen consumption, in fx\. per mg. of 

 dry weight per hour, of placental slices as a function 

 of the age of the placenta. The arrow at 40 weeks 

 indicates the range of the values obtained for term 

 placenta. 



