292 ADVENTURES IN RADIOISOTOPE RESEARCH 



formation of the corpuscles per day is less than 1% of the total corpuscles 

 present. 



As to the white of the egg, we find that at least a large part of its 

 phosphorus content is drawn from organic phosphorus compounds, 

 possibly from protein phosphorus. We arrived at this result by compar- 

 ing the specific activity of the phosphorus of the white of the egg with 

 that extracted from the shell. The latter derives its phosphate content 

 from the inorganic P of the blood plasma and is accordingly a convenient 

 measure of the activity of the latter. The shell is formed at about the 

 same time as the white of the egg, the great discrepancy between the 

 specific activity of the shell P and albumin P exclude the possibility 

 that they are of common origin. 



Summary 



By administering labelled sodium phosphate to laying hens the share of the 

 labelled phosphorus administered in the formation of the yolk, albumin and shell 

 of the egg can be followed by aid of radioactive measurements. The comparison 

 of the specific activity (activity per mgm P) of the phosphorus extracted from 

 blood plasma phosphatides with that extracted from the hver, the ovary, and the 

 \'olk phosphatides leads to the result that the buUc of the phosphatides of the 

 yolk originate in the Hver. It gets from the liver into the plasma and is then taken 

 by the latter to the ovary. 



No formation of phosphatides takes place in the oviduct. After the egg leaves 

 the ovary no more active phosphatide is formed. No formation of labelled phos- 

 phatide in the yolk can be ascertained in experiments in which an egg is placed 

 for a day in a labelled sodium phosphate solution. In the last mentioned experi- 

 ment in vitro shght amounts of labelled phosphorus are found in the yolk, appre- 

 ciable quantities in the white, and large amounts in the shell. 



The specific activity of the phosphatides extracted from the blood corpuscles 

 was found to be only 1/3 of that extracted from the plasma. Therefore, we conclude 

 that the phosphatides formed in the hver and other organs are carried to the 

 ovary by the plasma rather than by the corpuscles. The latter apparently play 

 no important role in this process. 



