EX('H.\NGK OK THOSPHOJM S IX TKETJI 



179 



The adivily of tlic cxlractiMl pulp was very weak and only amounted 

 to about 3"o ol lliat of Ihe ui)per incisors. Should the exchan^re of phos- 

 phorus in the ealcium phosphate of the teeth be very small, it is however 

 quite possible that the amount of labellcni phosphorus present in the 

 ])ulp would no longer be negligible (eomp. p. 20). 



While in the experiments described above emphasis was laid on the 

 investigation of the remote incisal end, in Ihe following experiment 

 we cut the proximal end of the incisor into small pieces and compared 

 their activity with that of the distal end. The results are seen in Table 1 1 , 

 I denoting ihe united parts nearest to the jaw of all four incisors (comp. 

 Fig. 3). 



^1 U 1,1 rn rri 



Fia. 3. Distribution oi" labelled phosphorus in the incisor of a rat 



killed 7 days after administration of the phosphorus. 

 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. 2.0 should read 2.8. 



Table 11. Distribution of Labelled 



Phosphorus, In.jected Subcutaneously, 



Ix THE Incisor after 7 days. Weight of the Kat 



ABOUT 200 GM 



Averag(> % of labelled P per mgm tissue = 0.0028, per mgm ash 

 0.0038. 



The investigation of the labelled P content of the head (A), the central 

 (B) and lower part (C) of the tibia gave the figures seen in Table 12. 



While in the proximal end of the incisor the phosphorus exchange 

 is much greater than in any part of the tibia, the exchange of the average 

 phosphorus atoms in the tibia is about 29% greater than that of the 

 average P atoms of the incisor; this is due to the fact that contrary 

 to the tibia a large part of the incisor exchanges phosphorus atoms 



12* 



