EXCRETION OF PHOSPHORUS 541 



that in the faeces. Vice versa, anything that favours solubihty of phos- 

 phate in the alimentary tract, augments absorption and increases urinary 

 phosphorus at the expense of the faeces. Thus, diets high in calcium 

 and low in phosphorus lead to high faecal output and phosphorus defi- 

 ciency, probably because the phosphate forms an insoluble precipitate 

 of calcium phosphate in the intestine. It has often been observed that 

 fatty acids, by diverting calcium from phosphoric acid, may release 

 the latter for absorption. Anything which tends to produce a more acid 

 medium in the intestine, exerts a favourable influence on the phosphorus 

 absorption. Thus the ingestion of hydrochloric acid increases the urinary 

 phosphorus at the expense of the faeces. The daily excretion of phosphate 

 in the urine of an adult in normal conditions varies from 0.3 to 2 gm 

 of P. A careful determination of the average daily phosphorus intake^^^ 

 of 25 college women has shown an intake of 1.40 gm, which is thus 

 somewhat higher than required by the Sherman Standard (1.32 gm). 

 In experiments^^), in which the subjects used, were students and an acid- 

 forming diet containing 780 gm, milk was administered, the daily phos- 

 phorus intake was found to be 1.98 gm. When as large an amount as 

 10.8 gm P was administered to a human subject, an output of 8.9 gm 

 was found, 79% of the latter being present in the urine and 21 % in the 

 faeces. About one fourth of the phosphate fed was stored^^\ In the early 

 hours of the day the rate of excretion in the urine is minimal^'*), and then 

 it rises during the course of the day, to reach a maximum at 4 or 5 in 

 the afternoon. The level of excretion is then maintained for the remainder 

 of the day and throughout the night. Within wide limits, there is no 

 relationship between the amount of urinary phosphate and urinary 

 volume. The rate of phosphate excretion is independent of the rate of 

 water elimination even when, owing to copious diuresis, the urinary 

 phosphate is below the level of the plasma phosphate<^). As to the phos- 

 phorus excretion in animals, we wish only to mention the following 

 data collected by us. Rats weighing about 230 gm excreted daily 28.7 

 mgm P; within 7 weeks the ratio urine P: faeces P varied between 1.3 

 and 2.4, the average being 1.6. 



^1^ R. E. Havabd and G. A. Reay, Biochem. J. 20, 99 (1926). 



^2> M. M. Kramer, M. T. Potter and J. Gillum, J. Nutrit. 4, 105 (1931). 



(3) \v. T. Salter, R. F. Farquharson and D. M. Tibbets, J. Clin. Inv. 11, 

 395(1932). 



(*) Comp. C. H. FisKE, J. Biol. Chetn. 49, 171 (1921); S. Bellac, J. Chaussin, 

 H. Langer and T. Ransox, C. R. 207, 90 (1938). 



(5) R. E. Havabd and G. A. Reay, Biochem. J. 20, 99 (1926). 



