112 O. J. Mai.m, R; Nicola ysen and L. Skjelkvale 



the absorption quickly reaches very high values. This result 

 has been confirmed in a number of other experiments. The 

 results achieved in the very old (thirty-one months) rats 

 have so far been confirmed in fifteen to twenty months old 

 rats. 



Vitamin D free diet 

 ma. Ca/day 



20 



jVit. D 20 m./day| 



absorbed 



total Ca loss 

 610 m^. 



640 ing. H 



-^640 — 



-4 



0.25 % 



0.04% 



leveb c£ 

 Ca in 

 the diet 



30(^ 

 A^e 51 weeks 



300^. body 

 85 we«ks 



wt. 



Fig. 1. The absorption of Ca in six female rats. (Ca intake 

 on the diet containing 0-25 per cent Ca, about 40 nig. daily.) 



The urinary Ca was measured throughout in the very old 

 rats. The daily output was about 0-5 mg. in the period of 

 deprivation. In the following two weeks it increased to about 

 2 mg. daily. Thus nearly all Ca absorbed was retained. The 

 loss of bone minerals suffered in the period of deprivation 

 could quickly be made good. 



