282 



ADVENTURES IX RADIOISOTOPE RESEARCH 



inorganic P of very high activity is piesent ahnost at once after injecting the 

 active sodium phosphate. The non phosphatide P of the yolk is partly inor- 

 ganic P which gets into the yolk in the early stage of the experiment when its 

 specific activity is very high; we mvist therefore consider the lecithin P and not 

 the non- lecithin or total P content as a proper measure of the growth of the 

 A oik. From the fact that the lecithin P of the 30—100 mgm yolks became active 



only to a very slight degree we 

 must conclude for example that 

 they had hardly grown within tlK> 

 last 28 hours. When discussing 

 the labelled let-ithin P (phospha- 

 tide P) present in blood and in 

 some of the organs we shall find 

 definite evidence that the yolk 

 lecithin is dra^^^l from the plasma 

 lecithin. 



It is of interest to remark that 

 the ratio of the total active leci- 

 thin content of small yolks, such 

 as would require 10 daj's or more 

 to attain completion, is a quanti- 

 tative measure of their relative 

 growth since the administration 

 of the labelled P. When, however, 

 comparing the lecithin P activity 

 of a small yolk which increases 

 its weight in the course of a da^- 

 only to a slight extent with that 

 of a large yolk growing at a rate of 

 few gm per day the ratio of the 

 total activities will not always be 

 a correct measuie of the growth 

 since the administration of the la- 

 belled P. It may happen (comp. 

 Fig. 2) that the giowth of yolk per 

 hour is larger at the end than in 

 the beginning of the experiment the latter process determining thus to a larger 

 extent the total growth within the time of experiment. From which it follows, 

 that if at the beginning of the experiment the specific activity of blood lecithin 

 happens to V)e greater than at the end, we underestimate tlie growth of the 

 large yoUc. 



It is, however, the determination of the slow rate of giowth of the small and 

 tiny yolks, often present in a very large number in the ovary, which can be of 

 special interest and whidi can hardly be determined by any method other than 

 that outlined above. 



Fig. 2. Increment of the weight 



of yolks in the coui-se of 1 2 da_\'S 



before completion of the yolk 



according to Gerhartz. 



Investigation of blood phosphorus 



Plasma and (corpuscles of the hens blood were separately investigated using 

 the experimental method described on page 276. The results obtained are seen from 

 Table 9 which contains data on the specific activity (activity per mgm P in percent 

 of that injected) and also the total phosphorus present in the hens blood under 



