392 



PHYSIOLOGICAL CHEMISTRY 



NEUTRAL SULPHUR COMPOUNDS 



Under this head may be classed such bodies as cystine (see page 75), 

 chondroitin-sulphuric acid, oxyproteic acid, alloxyproteic acid, uroferric 

 acid, methyl mercaptan, ethyl sulphide, thiocyanates and taurine 

 derivatives. The sulphur content of the bodies just enumerated is 

 generally termed unoxidized or neutral sulphur in order that it may not 

 be confused with the acid or oxidized sulphur which occurs in the 

 inorganic sulphuric acid and ethereal sulphuric acid forms. Ordinarily 

 the neutral sulphur content of normal human urine is 5-25 per cent 

 of the total sulphur content (see " Sulphur Partition" in chapter on 

 Metabolism.) The actual amount excreted may be 0.2-0.4 grams 



FIG. 126. ALLANTOIN, FROM CAT'S URINE. 



a and &, Forms in which it crystallized from the urine; c, recrystallized allantoin. (Drawn 

 from micro- photographs furnished by Prof. Lafayette B. Mendel of Yale University.) 



per day, calculated as SOs. Its origin is mainly endogenous. The 

 excretion is fairly constant for any given individual in spite of dietary 

 changes. In tuberculosis, cancer, cystinuria, etc., the amount may 

 be relatively or absolutely increased. 



NH.CH.NH 



ALLANTOIN, OC 



CO 



NH.CO NH 2 



AJlantoin is found in the urine of practically all mammals including 

 man. In human urine it occurs in very small amount (5-15 mg. per 

 day) whereas in the case of all other mammals investigated except 

 anthropoid apes, it is the principal end-product of purine metabolism 



