EXCHAXOE OF PHOSPHORIS TX TEETH 



17 



Table 9. Distribition in the Inci.sor after ."} DA'is. Lahelled 



PhOSPHORTS In.JECTEI) .Sl'Bt'rT.\NE()t'.SLY. 



Weight of the Rat abott 2()(t gm 



in Fig. 1 B. The result of this experiment is seen in Table 9 and the dia- 

 gram Fig 2. 



The content ol' labelled P varies between 0.01% ai the proximal end 

 and 0.000033% at the pulp-free distal end, thus diminishing by a factor 



10 mm 



Fig. 2. Distribution of labelled phosphorus in the int-isor of a rat 



killed 3 days after the administration of the phosphoius. 



The figures below give the relative amounts of labelled phosphorus 



present in 1 mgm of fresh tissue in the section in question. The 



figures above give the length of the .section in mm 



of 1/300. On comparing the activity of the ash obtained by igniting 

 the incisor the figures work out to be 0.015% and 0.000044% respec- 

 tively, corresponding to a factor of 1/340. The average content of labelled 

 P in 1 mgm tissue was found to be 0.0041%, in 1 mgm ash 0.0059%. 

 Fig. 2 shows both the location of the pulp and the distribution of the 

 lal)elled phosphorus. It is seen clearly that the bulk of the labelled phos- 

 phorus atoms are to be found in the vicinity of the pulp but an amount which 

 is far from being negligible reaches even the remotest part of the incisor. 

 In Fig. 2 we have inserted the relative abundance figures of the labellefl 

 phosphorus present in the different parts of the incisor. A part of the 

 first sector amounting to 1.4 mm. grew during the time which elapsed 

 between the injection of the labelled P and the killing of the animal; 

 the other parts were present before. Out of 204 parts of labelled phos- 

 phorus only 100 were found in the first sector and consequently not 

 more than 30 in the part actually grown, the remaining 174 or more 

 being at least partly located in the parts present before injecting the 

 phosphorus. 



1 2 Hevesv 



