278 ADVEJfTURES IX EADIOISOTOPP; RESEARCH 



the knowledge of the change of the labelled phosphate content of the hens blood 

 with time, it is for our present purpose sufficient to bear in mind that an initial 

 rapid decrease of the labelled inorganic P content of the plasma occur and be- 

 comes slower. 



In the first experiments described in this paper, in contrast to most of our 

 experiments, we administered large amounts of P, of the order of magnitude 

 of 100 mgm. The very strongly active phosphorus preparation (of a strength of 

 about 10" counts) used in these experiments was a generous gift of Professor 

 Lawrence and was prepared by the bombardment of few grams of red phosphorus 

 by liigh speed eleuterium ions generated in Professor Lawrence's powerful cyclo- 

 tron. The active P was thus mixed with a comparatively large amount of inactive 

 phosphorus. In the experiments to be described, in contrast to some other experi- 

 ments, the comparatively large amounts of phosphorus did not interfere, their 

 presence in the active preparation has even the advantage that we can fix exactly- 

 the limit within which the sensitivity of our indicator, the number of mgm of 

 total inorganic P indicated by 1 count activity, varied throughovit the experiment. 

 The 100 mgm P administered had an activity of 10** counts. If the labelled P had 

 not been diluted bj- non-labelled P of the organs we should have found after the 

 lapse of 28 hours, the time of the experiment discussed on page 276, a specific acti- 

 vity of the plasma blood inorg. P— activity per mgm P— amounting to about 

 1% of the total activitj^ administered. (The amount of inorg. P present in the 

 total plasma is only about 5 mgm and thus much smaller than the 100 mgm P 

 administered.) As seen from Table 9, however, only 0.01% was founel, showing 

 that from the inorganic P atoms present in the blood of the hen aftei- the lapse 

 of 28 hours only 1% were those actually administered, the rest being ones originat- 

 ing from different organs and partly also from the food taken within that time. 



We carried out three types of experiments: 



a) Administration of labelled sodium phosphate to a hen and investigation 

 of the eggs layed at different dates. 



h) Administration of labelled sodium phosphate, killing the animal, removal 

 of the yolks and investigation of these yolks, the blood, the liver and other organs. 



c) Experiments in vitro in which eggs weie placed in labelled sodium phosphate 

 solutions for few days and investigated as to what extent the labelled P penetra- 

 ted into the egg. 



We will first discuss experiments of the type a). 



a) Investigation of the labelled phosphorus content of eggs laid at 

 different dates 



We injected radioactive phosphorus as sodium phosphate subcutaneousl\- to 

 hens and investigated the radioactive phosphonis content of the different parts 

 of the eggs laid at different times. The first egg was layed 41/2 hours after admi- 

 nistering the radioactive (labelled) phosphorus. We found the albumin to contain 

 0.0015% of the 40 mgm of phosphorus injected, a similar amount 0.0014»o being 

 present in the ^'olk. As the total phosphorus content of the yolk was found to be 

 100 mgm and that of the albumin only 4 mgm, the specific activity (active phos- 

 phorus per mgm normal phosphorus) was twenty-five times larger on the albumin 

 than in the yolk. We found the lecithin phosphorus to be 53% of that of the total 

 phosphorus of the yolk and to be entirely inactive. No synthesis of lecithin mole- 

 cules took place in the yolk therefore within the 41/0 hours preceding the laying 

 of the egg, as in that case some active lecithin molecules should have been formed: 

 taking this fact into account the specific activity of the other than lecithin phos- 

 phorus present in the yolk works out to be thirteen times smaller than that of 



