recently been investigated by Northrup and Nelson (1916). It has 

 been known for some time that starch contained a small percentage of 

 phosphorus which could not be completely removed by washing, 

 dialysis or by repeated precipitations (Thomas 1914). Samec (1914) 

 believed that the phosphoric acid in starch was present in an ester com- 

 bination and he called it amylophosphoric acid. Northrup and Nelson 

 succeeded in isolating a new organic phosphoric acid from partially 

 hydrolyzed starch, corresponding to the formula C 17 H 33 19 P. The acid 

 is optically active, reduces Fehling's solution and on hydrolysis yields 

 glucose and phosphoric acid. 



The phosphorus compounds occurring in plant or vegetable 

 material may be divided, on the basis of our present knowledge, into 

 the following groups : 



1. Inorganic phosphates. 



2. Nucleic acid. 



3. Lecithin or phosphatides. 



4. Hexosephosphoric acid. 



5. Starch phosphoric acid and other combinations of organic 

 radicals with phosphoric acid. 



6. Inosite phosphoric acids or phytin. 



The inorganic phosphates will not be discussed in this paper. 



According to Osborne (1918), there is no evidence of the occur- 

 rence of phosphoproteins in plants although references are frequently 

 found in the literature to plant phosphoprotein. 



The inosite phosphoric acid, or phytin, is quantitatively the most 

 important phosphorus compound found in plants. The chemistry and 

 properties of this substance, as web 1 as closely related inosite phos- 

 phoric acids, will be particularly considered in this paper. 



A large number of investigations have been made regarding the 

 metabolism and utilization of organic phosphorus compounds in the 

 animal organism. This subject has been exhaustively reviewed by 

 Forbes and Keith (1914), to which reference is made. 



INOSITE PHOSPHORIC ACID OR PHYTIN 



In the excellent resume of the literature on the subject of inosite 

 phosphoric acid by Rose (1912) will be found an interesting histori- 

 cal sketch of the investigations which led up to the discovery of inosite 

 phosphoric acid. It may be stated briefly here that the first chemical 

 examination of the substance was made by Brandau under Pfeffer s 

 direction (1872), the object being to determine the constituents of the 

 aleuron grains which had been described and named earlier by Hartig 

 (1855). This investigation revealed the fact that the aleuron grains 

 from seeds, named "globoid" by Pfeffer, contained phosphorus, cal- 

 cium and magnesium. 



