122 F. H. SCOTT. 



when it was filtered. A definite volume of the filtrate was taken and 

 the phosphorus detennined after oxidation by the Neumann method 

 as modified by Plimmer. The phosphorus in this tannic acid filtrate 

 we term soluble phosphorus. The amount of inorganic phosphate in 

 the digest was determined by first filtering and then throwing down 

 the phosphate in a definite volume of the filtrate with ammonia and 

 magnesium citrate. That the organic substances present did not 

 inhibit the precipitation of the ammonium magnesium phosphate was 

 shown by the result of control experiments in which a definite amount 

 of inorganic phosphate was added to a sample before precipitation. 

 After the precipitate had been dried, burnt and weighed, and the 

 amount deducted for the quantity of phosphate added, the remainder 

 was found to correspond with the amount obtained from a sample of the 

 same fluid to which no inorganic phosphate had been added. The 

 action of acid in liberating the phosphorus from tissue will be seen in 

 the following tables. 



2N 

 TABLE I. Ox testis, fresh. 510 c.c, -p HNO 3 added to 170 grs. 



of tissue. Kept at 38. 



Mgms. PoO 5 in 50 c.c. of 

 digest as 'soluble' phosphorus 



Sample taken as soon as possible contained 43 '8 



,, 1 taken after 19 hours contained 59 - 2 



2 ,, 24 62-7 



3 43 64-1 



4 48 64-6 



5 67 65-2 



., 6 91 64-8 

 Total phosphorus in 50 c.c. =72-3 



In the above table two facts are to be noticed, first, the ease with 

 which most of the phosphate present is converted into ' soluble ' 

 phosphorus, and second, that there is a residue of phosphorus which 

 does not pass into the soluble state. The large amount of phosphorus 

 present in sample is partly due to the difficulty in obtaining the first 

 sample. The inorganic phosphate was not determined in this case at 

 the commencement, but 2 days after sample 6 was taken it was found 

 to be only 18 mgms. of P 2 O 5 in 50 c.c. Thus although the acid liberates 

 | of the phosphorus as ' soluble ' phosphorus yet only \ of it was present 

 as inorganic phosphate. Subsequent experiments show that this inor- 

 ganic phosphate is not derived from nucleins but from inorganic salts 

 originally present in the tissue. 



