744 APPENDIX. 



integration. It is always found in the juice of muscle. It is generally 

 decomposed in the blood into urea and kreatinin, and seldom, unless 

 under abnormal circumstances, appears as such in the urine. Treated 

 with either sulphuric or hydrochloric acid, it is converted into kreatinin; 

 thus 



C 4 H 9 N 8 2 = C 4 H 7 N 3 + H 2 0. 



It has been made synthetically by bringing together cyanimide and 

 sarcosine. 



Kreatinin, C 4 H 7 N 3 0, is present in human urine, derived from oxida- 

 tion of kreatin. It does not appear to be present in muscle. 



Uric Acid, C 5 H 4 N 4 3 , occurs in the urine, sparingly in human urine, 

 abundantly in that of birds and reptiles, where it represents the chief 

 nitrogenous decomposition product. It occurs also in the blood, spleen, 

 liver, and sometimes is the only constituent of urinary calculi. It is 

 probably converted in the blood into urea and carbonic acid. It gener- 

 ally occurs in urine in combination with bases, forming urates, and 

 never free unless under abnormal conditions. A deposit of urates may 

 occur when the urine is concentrated or extremely acid, or when, as 

 during febrile disorders, the conversion of uric acid into urea is incom- 

 pletely performed. 



Properties. Crystallizes in many forms, of which the most common 

 are smooth, transparent, rhomboid plates, diamond-shaped plates, hexa- 

 gonal tables, etc. Very insoluble in water, and absolutely so in alcohol 

 and ether. Dried with strong nitric acid in a water bath, a compound 

 is formed called alloxan, which gives a beautiful violet red with ammo- 

 nium hydrate (murexide), and a blue color with potassium hydrate. It 

 is easily precipitated from its solutions by the addition of a free acid. 

 It forms both acid and neutral salts with bases. The most soluble urate 

 is lithium urate. 



Composition. Very uncertain; has been however recently produced 

 artificially, but it is not easily decomposed; it may be regarded as diure- 

 ide of tartronic acid. The chief product of its decomposition is urea. 



Guanin, C 5 H 5 N 6 0, has been found in the human liver, spleen, and 

 faBces, but does not occur as a constant product. 



Xanthin, C 5 H 4 N 4 2 , has been obtained from the liver, spleen, thy- 

 mus, muscle, and the blood. It is found in normal urine, and is a con- 

 stituent of certain rare urinary calculi. 



Hypoxanthin, C 5 H 4 N 4 0, or sarkin, is found in juice of flesh, in the 

 spleen, thymus, and thyroid. 



Allantoin, C 4 H 6 N 4 3 , found in the allantoic fluid of the foetus, and 

 in the urine of animals for a short period after their birth. It is one of 

 the oxidation products of uric acid, which on oxidation gives urea. 



In addition to the above compounds and probably related to them, 



