184 



ADVEXTIKES IX RADIOISOTOPE RESEAECH 



The corresponding enamels weighed 29.3, 34.3 and 55 mgm. The 

 canine enamel was found to contain less than V'^q of the labelled P con- 

 tent of the corresponding dentine. 



In another experiment a strong preparation was administered in 

 three portions, 5 days, 2 days and 1 day before killing the animal, each 

 portion containing 40 mgm P. The results are seen in Table 20. 



Table 20. Cat Weighing 4 kgm.. Killed after 5 Days. 



Weight of 



teeth 

 in mgm 



Weight of 



ash 

 in mgm 



% of injected 



labelled P present 



in the teeth 



% of the labelled 

 P per 100 mgm 

 ash of the tooth 



Molar 323.3 [ 186.0 



Canine [ 422.2 274.3 



8 Incisors 172.5 1 117.5 



0.0027 

 0.0038 

 0.0021 



0.0015 

 0.0014 

 0.0018 



The enamel obtained is discussed on page 183. In investigating the 

 incisors of rats we I'ound the activity to be due almost exclusively to 

 the phosphate of the mineral constituents, the pulp being only slightly 

 active. In the earlier experiments conditions were however very diffe- 

 rent from those obtaining in the above mentioned case. The uptake of 

 labelled P in the teeth of a cat is much smaller than in the incisors 

 of a rat and correspondingly the ratio of labelled P in the plasma to 

 labelled P in the teeth is much larger in the case of the cat. Now a high 

 blood activity will lead to a comparatively high pulp activity and we 

 must expect a greater share of the pulp^ in the total activity of the tooth 

 in the case of cat teeth. To test this point we removed the pulp of some 

 of the canine teeth and compared the activity of the dissected and the 

 total canine. We found an activity ratio of 3 : 4, showing that a quarter 

 of the activity of the canines of a fully grown cat is due to the 

 pulp. 



A comparison of the figures of Tables 17 and 18 with those of 19 and 

 20 shows that the uptake of labelled P in young animals is greater than 



1 Human tooth pulp was found by H. C. Hodge, Proc Soc. Exp. Biol. Med. 

 35, 53 (1936) to contain 0.70% phospolipins besides other phosphorus compounds. 



