Origimilly published in the Svedberg p. 450. Uppsala (1944) 



22. RETENTION OF ATOMS OF MATERNAL ORIGIN IN 

 THE ADULT WHITE MOUSE 



By G. Hevesy 



From the Institute of Theoretical Physics, University of Copenhagen and the Badiiini 



Station in Copenhagen 



What percentage of the atoms present in the new-born organism is 

 retained during the later phases of life and what percentage is inherited 

 by the subsequent generations? An attempt was made to answer 

 these questions by following the fate of the phosphorus atoms in the 

 white mouse, radio-phosphorus being used as an indicator. 



The phosphorus atoms present as constituents of different compounds 

 in the body of the new-born animal are released successively from the 

 compounds in which they are present. The phosphorus atoms thus 

 released are either excreted or re-incorporated into various compounds 

 present in the body, the latter process being much more frequent. 

 Although, for the sake of simplicity, we speak of phosphorus atoms, 

 practically no phosphorus atoms but only phosphate radicals are released 

 from and built into such phosphorus compounds. The organism is sup- 

 plied with phosphorus in the form of phosphate radicals and the phos- 

 phorus atoms adhere, as far as is known, to their partners throughout 

 the numerous metabolic processes in which they participate. 



The white mice used in the experiment were kept on the following 

 diet. Wheat flour, oatmeal and a small amount of milk were administered, 

 while on alternate days only Cooley's standard food was provided. 

 Once a week, cabbage or lettuce was administered as well. 



About 0.1 mgm of labelled sodium phosphate with an activity of a few 

 microcuries was administered by subcutaneous injection to a pregnant 

 mouse. As a result of introducing radiophosphorus into the organism 

 of the pregnant mouse, we obtain offspring of which the phosphorus 

 contents were labelled. A litter consisted of about 8 offspring having 

 almost the same weight, as shown in Table 1. 



The radio-phosphorus contents of the offspring may therefore also 

 be expected to be almost equal. This fact makes it possible to determine 

 the total ^^P content of the offspring at any date by measuring the 

 total activity of any member of the litter. 



One offspring was killed shortly after birth and dissolved in concentra- 

 ted nitric acid. The phosphorus content of a known aliquot of the solution 



