324 HENRY A. MATTILL AND HELEN I. MATTILL 



A compilation and review of the information available in 1914 forms a 

 compendious monograph embracing about 3,000 titles, and it would seem 

 unnecessary, indeed, if not impossible to refer individually even to the 

 more important contributions before that time (Forbes and Keith). 



In inorganic form phosphorus is found in animal and plant tissues 

 chiefly in the form of K and Ca salts of phosphoric acid and in the organic 

 forms in the generally familiar classification as nucleoproteins, phos- 

 phoproteins and lecithoproteins or phosphatids. To these should be added 

 the phosphoric acid esters of carbohydrates and related substances which 

 may be found increasingly .important as investigation continues; for 

 example, a phosphorus-containing carbohydrate is regularly found as a con- 

 stituent of starch (Xorthrup and Nelson). 



The distribution of the different forms of P in the organs and tissues 

 has claimed the attention of several investigators recently and the resulting 

 outstanding facts are that inorganic phosphates make lip the greater 

 amount of muscle, bone and blood phosphorus (Heubner; Green wald(/), 

 that the important substance for muscular activity is a compound of lactic 

 and phosphoric acids which is derived from organic P compounds 

 (Embden), that in smooth muscle the protein P is more abundant than in 

 striated (Cost ant ino), that lack of P in the food affects first the in- 

 organic P of the bones and liver and that of the other organs only very 

 gradually. The brain and heart lose total P under no conditions of dieting 

 (Masslow(a)), exceptional ingest ion of P as phosphates seems to decrease 

 the P content of the central nervous system, although it does not seem to 

 influence the deposit of phosphatids in muscle and bone, the percentage 

 of which is remarkably constant throughout life; possibly it does affect 

 the nucleoproteins (Heubner). 



An estimate of the phosphorus requirement is rendered doubly difficult 

 because of the uncertainty which surrounds the question of the availability 

 of the different forms of phosphorus in foods. Unquestionably there is* 

 a difference between the phosphates and the organic P compounds both 

 in the rate and the percentage of absorption. Experimental studies in 

 which phosphates have been added to a diet poor in P can therefore hardly 

 be compared with those in which an ordinary mixed diet has been used. 

 Sherman found from a study of 05 balance experiments that the minimum 

 requirement averaged 0.88 g. P per day per TO kg. body weight, and he 

 considers 3.50 g. P 2 O 5 per day a sufficient intake. Berg maintained 

 equilibrium on 2.25 g. P 2 O 5 daily at the same time that Ca equilibrium was 

 maintained on 0.33 g. CaO, and he showed that the addition of 10 g. 

 CaHPO 4 to this diet not only resulted in no retention of either P or Ca, 

 but caused a loss of Ca from the body. Von Wendt on the other hand was 

 able to convert a negative CaO balance to a positive balance by the addition 

 of 3g. CaHPO 4 . Any definition of the P requirement without at the same 

 time taking into consideration the Ca supply, or vice versa, is unsafe. 



