288 ADVENTURES IN RADIOISOTOPE RESEARCH 



the specific at^tivity of the ovary phosphatide was found to be low, as low as 

 that of the yolk, proves definitely that the role of the ovary is not produc- 

 tion of phosphatides but their extraction from the blood plasma together 

 with other suitable constituents. The combination of phosphatides with proteins 

 giving the characteristic composition and consistency of the yolk, is 

 evidently one of its principal functions. In the experiment described above 

 the specific activity of the P of the yolk soluble in trichloracetic acid was 

 found to be 0.035, thus 1/4 5 part of that of the inorganic P of the plasma 

 the latter being 0.16. Making the assumption that most of the atad soluble P 

 originates from the inorganic P of the plasma we find a growth of the yolk amount- 

 ing to 1/45 part of its weight of 1.0 gm during the experiment. ^Miile the above 

 mentioned figure of Yii was, as ahead}- mentioned, a lower limit of the part of 

 the yolk newly formed within 5 hours, the figure of I/4.5 is a higher limit. A part 

 of the acid soluble yolk phosphorus was formed at an earlier stage when the speci 

 fie activity of the plasma inorganic P was appreciably higher than at the end 

 of the experiment, and as our calculation is based on the specific activity of the 

 plasma inorganic P at the end of the experiment it gives too high a value for the 

 amount of yolk formed during the experiment. 



The phosphorus of the white of the egg removed from the oviduct had a low 

 specific activity, namely 0.0013. This is an interesting result in view of the strong 

 activity shown by the phosphorus compovinds present in the plasma (comp. Table 

 13). A possible explanation of this result is that some of the phosphorus present 

 in the protein or other compounds of the oviduct tissue is utihsed to produce the 

 phosphorus compounds present in the white of the egg. In the course of five houi's 

 perhaps the compounds present in the tissue of the oviduct get labelled only to 

 a slight extent. An other explanation is that while the average plasma protein 

 P has a high specific activity 0.15 after the lapse of five hours, the specific activity 

 of the phosphorus of one of the components of the protein mixture might be low. 

 We are now engaged in the investigation of the origin of Ihe phosphoius 

 present in the white of the egg. 



Table 13. — Specific Activity of 

 Plasma Phosphor rs 



Fraction Specific activity 



Inorganic P 

 Lecithin P . 



(I. If) 



(I. ()()'.) 



Protein P <I.14 



c) Experiments //( vitro 



We placed eggs in a neutral physiological sodiumphosphate solution containing 

 30 mgm P for 24 hours and investigated the activity of the different parts of the 

 eggs, the results being seen in Tables 14 and 15. 



The comparatively high labelled P content of the shell is due to phosphate 

 exchange processes between the large shell surface and the solution and possible 

 also to the formation slight amounts of calcium phosphate trom the carbonate 

 of the shell. An investigation of the activity of the lecithin extracted from the 

 yolk gave an entirely negative result, this in agreement with the observation 

 recorded on p. 279 that after the egg left the ovary no more lecithin formation 

 takes place. 



