CHEMICAL BASIS OF THK ANIMAL BODY 171 



Thus parabanic acid (oxalyl-urea) is readily formed by the action 

 of phosphorus oxychloride on a mixture of urea and oxalic acid : 



NH CO 



MI, CO. OH CO 



C0 \ 1 = J 



NH a + CO.OH NH CO-f2H,0. 



When the close chemical relationship of urea to uric acid is 

 taken into account, the statement that those substances which 

 when introduced into the body of a mammal lead to an increased 

 excretion of urea, when introduced into the organism of birds are 

 converted into uric acid, 1 needs excite no surprise. There is fur- 

 ther distinct evidence, already referred to under urea, that tin- 

 conversion is affected in the liver. 2 "VYr k\\<>\\- nothing as y.-t a- 

 to the cause of the slight divergence of metabolism which leads 

 to the preponderating formation of urea in mammals and of uric 

 acid in birds and reptiles. It is certainly not due, as some have. 

 supposed, to insufficient oxidation in the latter, since the excretion 

 of uric acid is not increased in mammals by artificial disturbance 

 of the respiratory interchange, 3 and it is exactly in birds that the 

 most active oxidational changes, as shown by their higher tem- 

 perature, is observed. Bearing in mind how readily uric acid 

 yields urea as one product of its oxidational decomposition, it has 

 been supposed that a good deal more uric acid is formed in tin- 

 mammalian body than is excreted in the urine. In support of 

 this view it may be pointed out that uric acid when introduced 

 into mammals is largely excreted as urea, and that some of the 

 known products of the artificial ox i da t inn of uric acid are occa- 

 sionally found in their urine, e.g. oxalic acid, oxaluric acid 

 (hydrated parabanic acid), and allantoin. 4 The latter substance 

 is apparently increased (?) by the administration of uric acid. 6 



3. Oxaluric acid. C,H 4 Nj0 4 . (Hydrated parabanic acid.) 



Occurs in minute traces in normal urine, from which it is ex- 

 tracted by filtering a large quantity of urine very slowly through 

 a relatively small amount of animal charcoal. The charcoal after 

 being washed with distilled water is extracted with boiling alcohol, 

 to which it yields the oxaluric acid as an ammonium salt. The 

 free acid is a white crystalline powder, not very soluble in water : 

 it- alkaline salts are readily soluble. 6 



1 For liti-ritiire nee Bunge, Phi/iiol. path. Chrmistrv, i>. .141. Horl>:uv 

 Mnnatsf.fl / Cl.rm. Bd. X. (1889), S. 624. Sit:l>. d. HW. Akad, Bd. xcviu. (1889), 

 3 A I.- 



.-.I-.. -..!: Srhnuler, Arch. f. Phyiiol. 1880. Suppl.-Bd. S. 113. Ludwig'a 

 Feitsrhritf, ISH;. S. 98. 



Senator. Vir. -how's Arrh. B<1. xi.n. (1*68), S. 35 



Salkowski u. Ixsnbe. Die fshre vom I/arn (1882), S. 100. 



8alkow*ki. lirr. ,1. d. rhrm. tlrvtt. I-;., > 71'J. 1878. 8. 500. 



For .!. 'tails nee Hoppe-Seyler, Phyt.-path. Anal. 1832, S. 159. Neubaner u. 

 Vogel, Jftinxinalyte, 189O, S. 239. 



