RADIOACTIVE INDICATORS IN BIOCHEMISTRY 



973 



The above-mentioned lack of extra-ovarian formation of labelled 

 phosphatide in the yolk is also brought out in experiments with incubated 

 fertilized eggs into which labelled phosphate was injected^^a). While the 

 foetal phosphatides present in such eggs have a high ^ap content, the 

 remainders of the yolk still present in such eggs do not contain significant 

 amounts of labelled phosphatides, as seen in Table 4. The slight activity 

 of yolk phosphatides, which increases with age of the embryo, is possibly 

 caused by influx from the embryo into the yolk of a small amount of 

 labelled phosphatides or of the enzymes responsible for resynthesis of 

 phosphatides. 



Table 4. — Specific Activity oi Phos- 

 phatides EXTBACTED FROM EmBRYO 

 AND Residual Yolk of the Hen's 

 Er;o 



Similar considerations were applied by Aten^^") to the study of the 

 origin of the milk phosphatides in the goat. Table 5 demonstrates that 

 at least most of the phosphatide molecules of the milk are not those 

 which passed from the blood plasma into the milk, but those which 

 had their origin in the milk gland, the phosphatides of the milk being 

 much more active than those of the plasma, but less active than those 

 of the milk gland. 



The following scheme represents the course of phosphatide transport 

 in laying hens and in lactating goats^^"\ 



Table 5. — Activity of Phosphatide Phosphorus of Milk and Organs of a Goat^" 



^29)Hevesy, Levi and Eebbe, Ihid. 32, 2147 (1938). 



(30) Aten, Isotopes and Formation of Milk and Egg. Diss., Utrecht (1939); Aten 



and Hevesy, Nature 142, 111 (1938). 



