40 METABOLISM OF ORGANIC AND INORGANIC PHOSPHORUS. 



amounts of the two substances metabolized by the system, but this 

 does not hold in all cases. Rabbit No. 2, for example, which died, 

 shows a much larger amount of katabolized nitrogen and phosphoric 

 acid, as indicated by an increased elimination through the kidneys, 

 but this does not indicate an increased metabolism of these two sub- 

 stances. The ratio of nitrogen to phosphoric acid excreted in the 

 feces shows equal average figures for all the rabbits, excluding the 

 figures for No. 2. If the figures for rabbit No. 2 are included, the 

 average ratio is lower for the rabbits fed inorganic phosphorus. The 

 bulk of the nitrogen (60 to 78 per c^nt) is eliminated by the kidneys, 

 whereas, on the other hand, only 27 to 50 per cent of the phosphoric 

 acid is thus eliminated. The percentage of absorbed nitrogen which 

 was retained in the system is the same for rabbit No. 1 as for the 

 average of Nos. 3 and 4, receiving inorganic phosphorus. 



PHOSPHORUS BALANCES. 



The study of phosphoric acid metabolism raises many questions, of 

 which the following are especially important: 



(1) How is the phosphoric acid, ingested in different forms, taken 

 up by the body? 



(2) How is the phosphoric acid changed in the body? 



(3) In what manner is the phosphoric acid eliminated from the 

 body? 



Many investigators have attempted to answer some or all of these 

 questions, but no definite answer has been obtained. The generally 

 accepted idea is that the phosphoric acid ingested in different forms 

 is taken up by the body partly in various forms of organic combina- 

 tion and partly, also, in the inorganic or phosphate form. Most of 

 the organic phosphorus taken up by the body that absorbed from 

 the intestines is changed to the inorganic or phosphate form, and 

 all such phosphorus is eliminated in the urine as phosphates. This 

 idea that organic phosphorus compounds are more valuable than 

 inorganic combinations of phosphoric acid has been promulgated in 

 the medical literature during the past few years. Nevertheless, many 

 practicing physicians continue to prescribe the inorganic forms, not 

 only of phosphorus, but of iron, calcium, magnesium, etc. Yellow 

 phosphorus is given solely as an alterative. 



As the extent of the elimination of phosphoric acid is largely 

 dependent upon the character of the food and the absorption of the 

 phosphates in the intestines, it is apparent that the relationship 

 between the nitrogen and phosphoric acid in the urine can only be 

 approximately constant with a certain uniform food. Thus, on feed- 

 ing dogs with an exclusive meat diet, as observed by Voit, a when the 



Cited by Hammarsten, A Textbook of Physiological Chemistry, rev. ed., New 

 York, 1908. 



