254 THE URINE. 



gen and 0.00542 gramme of alloxur bases. In every case an accu- 

 rate record must, of course, be kept of the amount of urine and 

 filtrate used. 



Oxalic Acid and Oxaluric Acid. 



Of the origin of oxalic acid and oxaluric acid, both of which may 

 oe regarded as normal constituents of the urine, but little is known. 

 The former is supposedly present as a calcium salt, which is held 

 in solution owing to the presence of diacid sodium phosphate, but 

 readily separates out on standing and is then frequently encountered 

 in urinary sediments. Here it generally occurs in the very charac- 

 teristic envelope or dumb-bell forms, and can be readily distin- 

 guished from other constituents by its insolubility in acetic acid, 

 and its solubility in hydrochloric acid. Its amount normally varies 

 between 0.02 and 0.05 gramme. Oxaluric acid, on the other hand, 

 exists in the urine as an ammonium salt and is not found in sedi- 

 ments. Its amount is even smaller than that of oxalic acid. 



As many articles of food, such as asparagus, spinach, grapes, 

 apples, etc., contain oxalic acid in not inconsiderable amounts, it is 

 supposed that a certain fraction of the oxalic acid of the urine is 

 referable to this source. We find, as a matter of fact, that in the 

 asparagus season larger amounts are eliminated than at any other 

 time of the year. But it has also been noted that oxalic acid does 

 not disappear from the urine when the diet consists exclusively of 

 albumins and fats, and that during starvation also oxalic acid can 

 still be found. We are consequently forced to the conclusion that 

 a certain amount of the substance must originate in the tissues of 

 the body. We know, indeed, that oxaluric acid is closely related to 

 uric acid, and can be decomposed into urea and oxalic acid, as is 

 shown by the equations : 



CO NIL 



(1) C 5 H 4 N 4 3 + O -f H 2 = CO \C + CO(NH 2 ) 3 

 Uric acid. / 



CO NH/ 

 Alloxan. 



CO NH V 



|\ CO NH V 



(2) CO >CO + O >CO + CO, 



| / CO NH X 



CO NH/ Parabanic acid. 



Alloxan. 



CO NH V CO NIL 



(3) | >CO + H 2 O = | >CO 

 CO NH/ COOH.NH/ 



Parabanic Oxaluric acid, 



acid. 



CO NH X CO OH /NHj 



(4) | >CO + H 2 O = | + CO< 

 COOH.NH/ CO OH \NH 2 



Oxaluric acid. Oxalic acid. Urea. 



