PROGRESS OF THE ISOTOPIC METHODOLOGY 1021 



With increasing atomic mass the isotope effect decreases, it can, 

 however, be still noticeable for carbon. The error incurred by considering 

 "C as a correct indicator of i^c can be estimated by applying both i^c 

 and 13C as tracers, as tritium and deuterium are applied in the above 

 mentioned case. 



That the atoms building up the living organism are replaced in time 

 is common knowledge. The possibility of measuring the rate of their re- 

 newal and of following the path they take is a recent advance. A task 

 not easy to perform due to the reasons mentioned above and often 

 the lack of knowledge of the decisive precursor or precursors. New 

 possibihties of experimental attack stimulate our thoughts and lead them 

 into new channels. Problems come into the focus of interest which were 

 not considered previously. Here lies possibly the main importance of the 

 introduction of the method of isotopic indicators. 



To demonstrate that the notion of renewal of body constituents is an 

 ancient one, I beg you to permit me to read a statement made in the 

 thirteenth century by one of the greatest sons of this venerable and 

 beautiful country, Thomas of Aquina. What is to happen, asks the 

 samt, to a man who never, throughout his life, ate anything but human 

 llesh, and whose parents did likewise ? It would seem unfair to his vic- 

 tims that they should be deprived of their bodies at the last day as a 

 consequence of their greed; yet, if not, what will be left to make up their 

 body? I am happy to say that this difficulty, which might at first sight 

 seem insuperable, is triumphantly met. 



The identity of the body, St. Thomas points out, is not dependent on 

 the persistence of the same material particles; during life, by the process 

 of eating and digesting, the matter composing the body undergoes per- 

 petual change. The cannibal may, therefore, receive the same body at 

 the resurrection, even if it is not composed of the same matter as was 

 in his body when he died. 



References 



1. O. Chievitz and G. Hevesy, Nature 136, 7541 (1935). 



2. J. H. Lawrence and K. G. Scott, Proc. Soc. Exp. Biol. Med. 40, 694 (1939). 



3. G. Hevesy, L. Hahn and O. Rebbe, Danske Videnskab. Selskab Biol. Medd. 

 14, 3 (1939). 



4. J. G. Hamilton and M. H. Soley, Amer. J. Physiol. 127, 557 (1939). 



5. A. B. Hastings, Proc. Int. Conf. Geneva 10, 417 (1956). 



6. D. Stetten, Jr., Brookhaven Symp. of Biology 5, 85 (1952). 



7. M. Miller, A. Shipley, W. Shreeve, N. Baker, J. W. Craig, Tmm-. 

 Assoc. Amer. Physicians 68, 199 (1955). 



8. R. B. Chodos, J. F. Ross, L. Apt, M. Pollycove and J. Halkett, Proc. 

 Internat. Conf. Geneva 10, 373 (1956). 



