THE URINE. 359 



rated from the precipitate by washing are dissolved in boiling 

 water with the addition of some animal charcoal, and filtered while 

 hot ; then acidify the filtrate faintly with hydrochloric acid (so as 

 to keep the phosphates in solution) and allow it to crystallize. Al- 

 lantoin is detected in human urine by the method first suggested 

 by MEISSNER. It consists chiefly of the following points: Pre- 

 cipitate the urine with baryta- water, filter, remove the baryta with 

 sulphuric acid, filter, precipitate the allantoin with Hg01 2 in alka- 

 line solution, decompose the precipitate with sulphuretted hydro- 

 gen, concentrate strongly, purify the crystals which separate by 

 recrystallization, and lastly prepare the silver combination. 



Xanthin Bodies. The xanthin bodies which habitually occur 

 in human urine are xantliin, hypoxanthin (SALOMON), guanin 

 (POUCHET), carnin (POUCHET), and the newly-discovered bodies 

 paraxanthin (THUDICHUM, SALOMON) and heteroxanthin (SALO- 

 MON). The quantity of these bodies in the urine is very small. 

 The quantity of xanthin bodies in the urine is increased especially 

 in leucaemia, in which disease adenin is also found in the urine 

 (STADTHAGEN). Xanthin also occurs as a constituent of a variety 

 of rare calculi (MARCET). It is also sometimes found as a constitu- 

 ent of urinary sediments (BENCE JONES). 



Paraxanthin, GMIp^Oa (dimethylxanthin), and heteroxanthin, C 8 HN 4 O2 

 (methylxanthin), do not give the xanthin reaction with nitric acid and alkali, 

 but give WEIDEL'S reaction (see page 50). They differ from other xanthin 

 bodies by forming crystalline combinations with alkalies, which are diffi- 

 cultly soluble. Amorphous heteroxanthin separates on neutralizing the so- 

 dium combination, but paraxanthin, on the contrary, separates in a crystalline 

 condition. Paraxanthin gives an easily-soluble combination with hydro- 

 chloric acid, while heteroxanthin forms an insoluble, beautiful crystalline 

 combination. 



In preparing xanthin bodies from the urine, it is supersaturated with 

 ammonia and precipitated by a silver-nitrate solution. The precipitate is 

 then decomposed with sulphuretted hydrogen. The boiling-hot filtrate is 

 evaporated to dryness and the dried residue treated with 3# sulphuric acid. 

 The xanthin bodies are dissolved, while the uric acid remains uudissolved. 

 This filtrate is saturated with ammonia and precipitated by silver-nitrate solu- 

 tion. The different xanthin bodies may be separated from each other by 

 treating the silver precipitate with boiling-hot nitric acid of a sp. gr. of 1.1 

 (see page 51). 



Hippuric acid, or BENZOYL-AMIDO ACETIC ACID, C 9 H 9 N0 3 or 

 C 6 H 5 .CO.NH.CH 2 .COOH. This acid decomposes into benzoic acid 

 and glycocoll on boiling the urine with mineral acids or alkalies, 

 this also takes place in putrefaction. The reverse of this occurs 

 if these two components are heated in a sealed tube, according 



