VTIOSVHOKI'S METABOLISM TX KATS 151 



bones is a dynamic process, the bone continuously taking up phosphorus 

 atoms which are partly or wholly lost again, and are replaced by other 

 phosphorus atoms. In the case of an adult rat, about 30 per cent of 

 the phosphorus atoms deposited in the skeleton were roniOA(>d in Ihe 

 course of twenty days. 



In another set of experiments we investigated the different parts 

 of the skeleton. No conspicuous differences in the active phosphorus 

 content could be found, with the exception of the teeth. The front teeth, 

 which grow rapidly in rats, contained a larger part of the 2 mgm phos- 

 ])horus taken than the average of the whole skeleton, the ratio being 

 about 10 : 1 in the case of adult and 6 : 1 in that of half-adult rats, 

 whereas the molar teeth took up less than the average per gram of the 

 skeleton, the ratio being 1 : 2 in the most extreme case. A detailed 

 account of these and further results will be published elsewhere. 



