EXCHANGE OF PHOSPHORt'S IN TEETH 



189 



relative radioactive units we can estimate that about 1.8 -lO^ were 

 absorbed. As is seen in Table 21/6 relative units were found in a fairly 

 well preserved tooth on an average, showing that about 1 : 300.000 

 parf of the labelled phosphorus atoms enter a single tooth; in the case 



b) Necrotic C r o w n s 



c) Almost normal roots 



d) Almost normal crowns 



of a 16 years old boy about 1 : 200 000 was found. In the latter case 

 an activity of only 0.5 units (counts per minute) was shown by a 

 single tooth, and the estimate was accordingly only a very rough 

 one. From the above result W follows that about 1 : 300,000 part 

 of the phosphorus taken up with lli(> foot! finds its way into each tooth 

 of an adult. 



