130 Claude A. Villee 



in Warburg respirometer vessels at 37° in an oxygen atmo- 

 sphere. The composition of the incubation medium, expressed 

 in millimoles per litre, was K + 50, Na + 80, Mg + + 10, phosphate 

 40, Cl~ 100, pyruvate 10 and glucose 11-1. In alternate 

 vessels, either the glucose or the pyruvate was labelled with 

 14 C. The initial pH of the medium was 6 • 8 and the pH after 

 incubation was 6*8 ±0-1 (determined by glass electrode). 

 Other slices of the placentas were used for determination of 

 initial glycogen content and of wet weight : dry weight ratios. 



After a two hour incubation, the slices were removed, 

 weighed, and analysed for glycogen. Aliquots of the incuba- 

 tion medium were analysed for glucose (Nelson, 1944), 

 pyruvate (Friedemann and Haugen, 1943), and lactate 

 (Barker and Summerson, 1941). The respiratory C0 2 was 

 recovered from the alkali in the centre well and converted to 

 BaC0 3 , then its 14 C content was measured with a windowless, 

 proportional flow counter (Robinson, 1950). Glucose was 

 isolated from other aliquots of the incubation medium, after 

 the addition of 10 mg. of carrier glucose, as the glucose 

 phenylosazone. This was washed, recrystallized, washed 

 again, and its radioactivity was measured with the flow 

 counter. Pyruvate was isolated from the other aliquots, after 

 the addition of 10 mg. of carrier pyruvate, as the 2 : 4-dinitro- 

 phenylhyrazone. This was washed seven times with alcohol 

 and water, then its radioactivity was measured with the 

 proportional flow counter. Aliquots of the glucose obtained 

 from the tissue glycogen were converted to glucosazone for 

 radioactivity determinations. 



From these measurements one can estimate the net amount 

 of glucose utilized or produced, the net amount of pyruvate 

 utilized, the net amount of lactate produced, the amounts of 

 glucose and pyruvate carbons metabolized to C0 2 , the net 

 amount of glycogen produced or utilized, the amounts of 

 glucose and glycogen made from pyruvate, and the amounts 

 of glycogen and pyruvate made from glucose. 



Preliminary experiments showed that there was no detect- 

 able difference in the metabolism of slices from the chorionic 



