392 ADVENTURES IX RADIOISOTOPE RESEARCH 



and subsequent incorporation of labelled phosphate into the organic 

 compounds of the muscle of the frog is much greater than the tempera- 

 ture coefficient of the formation of apatite crystals. 



EXCRETION OF LABELLED P 



In a few cases, we determined the percentage ^^P which was excreted 

 by the kidneys of the frog. In one experiment, 1.5 cc. 0.6 per cent sodium 

 chloride solution containing 0.008 mgm P as phosphate was injected 

 into the lymph sack of the frog weighing 55 gm and kept at 18° . Urine 

 was collected during 14 hours and the ^^P content of the urine was 

 determined. It was found to make out 10.6 per cent of the ^-P injected 

 while, in other experiments, 7.1 and 5.8 per cent, respectively, was 

 found. 



UPTAKE BY THE FROG OF ^^p FROM A SOLUTION CONTAINING 



LABELLED SODIUM PHOSPHATE 



A frog weighing 88 gm was kept at 18° in 100 cc. 0.6 per cent sodium 

 chloride solution containing 4 mgm labelled P as sodium phosphate. 

 The solution was renewed every day. After the lapse of 21/2 days, the 

 frog was washed, killed and its P content extracted. It was found to be 

 695 mgm or 7.9 mgm per gram of fresh weight of the frog. The specific 

 activity of this P was found to constitute 1/450 of the specific activity 

 of the P of the solution in which the frog was kept. Thus, in the course 

 of 2I/2 days, 1/450 of the total P of the frog was replaced by solution P. 

 We investigated, furthermore, the activity of the inorganic P extracted 

 from the liver of the frog which was found to show a specific activity 

 amounting to 0.99 per cent of the specific activity of the solution P. 

 It was, thus, 4.5 times more active than the average P of the frog. 



RATE OF RENEWAL OF THE PHOSPHORUS COMPOUNDS IN THE 



MUSCLE 



In the preceding sections, experiments were described in which the 

 percentage of the administered ^sp present in the skeleton and the 

 muscles was determined. In the following, we wish to discuss the rate 

 at which the organic phosphorus compounds present in the muscles 

 of the frog are renewed. We shall consider those cases of renewal^^ 



^^) It is conceivable that molecules are renewed whithout the spUtting off and 

 reincorporation of phosphate group. 



