224 



ADVENTIKES I.V RADIOSIOTOPE RESEARCH 



moderate changes in heteiophylous values could be detected. In our experiments, 

 no effect on growth or fertility due to the presence of ^^Qa could be observed. 

 Our main litter size was 5.7. As shown by Russell(^^\ the litter size of mice at 

 term is reduced as a result of irradiation during preimplantation stages with 

 100 r or more, and when exposed shortly after implantation, by a minimum dose 

 of 200 r. 



The composition of standard cakes fed to our mice is seen from Table 2. 



RESULTS 



The results of experiments in which mice born from mothers kept 

 on a *^Ca diet for weeks prior to and after parturition, and continuously 

 kept on a ^^C'a diet till they reached an age of about 100 days, thus 

 were fullygrown, are shown in Table 3. 



The mean conservation of *^Ca by the uniformly labelled skeleton 

 of the mice in the course of 390 days, representing a mean value of the 

 duration of the experiments, works out to be 64.7 ± 7.34 per cent, the 

 standard error of the mean being 2.78. If we disregard the last experi- 

 ment in which the mice were kept on a high calcium diet, the mean 

 value is 67.2 ^ 7.86 per cent, the standard error of the mean being 

 3.23. Thus, -/g of the calcium atoms present in the skeleton of the out- 



o 

 U 



too 



200 



300 

 days 



400 



SCO 



600 



Fig. 1. Loss of *^Ca, obtained from labelled mother at biith, during 



lifetime of the mice. Each point indicates the ^^Ca content of 



another member of the litter killed at the stated time 



