PATH OF ATOMS TiriiOTOlI (JEXEHAIIOX.S 239 



of the body calcium is located in the skeleton. The skeleton is therefore 

 able to preserve an important part of its building materials. However, 

 only a fraction of this calcium is available for Ihe structure of the body 

 of the descendants. 



FATE OF WATER MOLECULES 



The calcium and phosphorus atoms of the ancestors of the mouse 

 (similar conditions should be valid for human beings) are traceable 

 in a long series of generations in the descendants. However, the watcn- 

 molecules that the mother transmits to the descendants disappear 

 during the life of the first generation. 



Shortly after the discovery of heavy water, we were able to determine, 

 thanks to the support of H. C. Urey, who discovered this isotope, the 

 half-life of water molecules in the human body. We found that this 

 amounts to about 10 days in the body (17) for normal water intake. 

 The half-life depends on the amount of water consumed. Schloerb 

 and his co-workers (18) also found recently a half-life of 10 days with 

 a normal daily intake of 2.7 liters. In the case of a rather large daily 

 water intake of 12.8 liters, the lifetime fell, however, to 2.5 days. In the 

 case of a normal water intake, after 810 days not a single molecule of 

 the 2x10^" water molecules originally present remains in the human 

 body. 



The half-life of water molecules in rats was determined to be 2.5 

 to 3.5 days. In the mouse it should amount to about 2.5 days. After 

 340 days, therefore, not a single maternal water molecule is present 

 in the mouse. 



Owing to the large part that the element calcium plays in the devel- 

 opment of the skeleton, it is preserved best in the descendants. However, 

 even of this element, not a single atom of the ancestors is present in the 

 11th and 12th generations. This evidence illustrates the independence 

 of the hereditary pattern from an atomic share of the forefathers. It is 

 well-known that the hereditary pattern depends on the ability of the 

 organism to group in atoms, molecules, and higher cellular units in a 

 certain manner. A protein composed of 20 different amino acids and 

 having a molecular weight of 100,000 is able to appear in more than 

 10^270 isomers, as calculated by Staudinger (19). Therefore, incompar- 

 ably more types of proteins can exist than the number of water molecules 

 (10^6) which are present in the oceans of the world. Since hereditary 

 patterns are tied to the reproducibility of individual proteins or nucleo- 

 proteins, there is room for new individual hereditary patterns as long 

 as the number of human beings has not reached 10^-"" or even a larger 

 figure. 



