236 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 8 



1 . The role of phosphorus in bodily metabolism. 7 Phosphorus is an 

 extremely important element to both plants and animals; phosphates 

 appear in the teeth and bones, and the internal organs contain phos- 

 phorus in the form of organic compounds, such as the phospholipids. 

 Many important questions arise, some of which can be answered by 

 chemical methods and some not. How much of the phosphorus intake 

 at a given time actually reaches the bones and teeth? How long after 

 intake does it arrive at a given point? How rapid is the replacement? 

 By what path through the bodily organs does it arrive? How are all 

 of these things affected by abnormal conditions of diet or of disease? 

 All of these questions and more can be answered by administering 

 radiophosphorus — in the food or otherwise — and then following the 

 radioactivity as it appears and disappears in various organs, the blood, 

 the bones or teeth. Kadiophosphorus (P 32 ) can be made in fairly 

 strong samples by deuteron bombardment of ordinary phosphorus. 

 The radiophosphorus can be combined into any compound after it is 

 activated, and can, therefore, be fed or injected in the most convenient 

 form. The half -life of P 32 is about 14.8 days, so the activity of a given 

 strong sample may be followed for many months. It decays with the 

 emission of an electron, going to S 32 which itself is probably harmless 

 but in any case would be formed in amounts far too small to produce 

 observable effects. By periodically testing the activity of samples 

 taken from various parts of the body — either during the life of the 

 animal or after killing and ashing — the amount and rate of phosphorus 

 arrival may be determined with considerable precision. The many 

 possibilities are sufficiently obvious as to require no further discussion 

 before this group. Some work along this line has already been under- 

 taken at various laboratories, with preliminary results which show 

 clearly the power, accuracy, and feasibility of the method. Some 

 surprising results concerning phosphorus mobilization during certain 

 diseases have already been indicated. I shall have to leave them to be 

 discussed by those more familiar with biology than I am. 



It is evident that similar studies could be made with almost any 

 other element of interest; calcium, potassium, iodine, iron, etc. The 

 only question which arises is whether there exists a radioactive isotope 

 of the element in question whose period is sufficiently long to make the 

 studies feasible. Here, of course, the physicist is somewhat helpless. 

 He can make radioactive isotopes at will, but he has no control over the 

 period of the resulting product; he must take what comes. Each 

 isotope has its own characteristic period, determined by its own 

 nuclear instability. The only hope is, if suitable periods of certain 

 elements are not now known, that new isotopes will some day be 

 discovered which are better adapted for such work. Nature has been 



7 The author is indebted to Dr. Wm. F. Bale of the University of Rochester School of Medicine for out- 

 lining the uses of radiophosphorus. 



