450 PHYSIOLOGY. 



Oxalic acid appears to be derived from outside the economy, 

 mainly from the ingestion of vegetable foods, as sorrel, lemons, rhu- 

 bar.b, etc. It may also result from incomplete oxidative processes. 



Creatinin occurs in the urine in the average daily amount of 0.9 

 gram. Its sources are believed to be: (1) the creatin of muscles 

 formed by the subtraction of a molecule of water and (2) flesh foods. 

 If creatin be fed to animals it appears as creatinin in the urine; 

 however, if it be injected intravenously it appears in the urine as 

 creatin; so that it is very improbable that the kidneys are con- 

 cerned in its manufacture. 



Next to urea, it is the most important nitrogenous body in the 

 urine. The absolute quantity of creatinin eliminated in the urine on 



a meat-free diet is a con- 

 stant quantity, different 

 for different individuals 

 but wholly independent 

 of quantitative changes in 

 the total amount of nitro- 

 gen eliminated. The chief 

 factor determining the 

 amount of creatinin is the 

 weight of the body and 

 Fig. 172. Effect of Xanthin on Muscle Curve, amount of fat it contains. 



Causing an Extra Contraction during the 

 Relaxation. (J. F. ULMAN.) 



IK 

 is 



product of metabolism of 

 muscle albumin. Creatinin, like uric acid, has an exogenous and 

 -endogenous origin, according to Folin. Creatinin is increased in fever. 

 Creatinin is a measure of the physiological catabolism of muscular 

 tissue. Xanthin, hypoxanthin, leucin and tyrosin, and traces of allan- 

 toin are sometimes formed in the urine, where they represent nitro- 

 genized bases of albuminoid retrogression. 



Ammonia. The urine always contains a small amount of 

 ammonia, on an average about half a gram. If you give carbonate of 

 .ammonia by the mouth it increases the urea, but not the ammonia in 

 the urine. If, however, a more stable ammonia compound is given, as 

 ammonium chloride or benzoate, then it is not converted into urea, but 

 is excreted as chloride or benzoate or ammonium. The previous trans- 

 formation of ammonia salts into a carbonate is a necessary condition 

 for the ammonia to be converted into urea. 



The body defends itself normally against the acids generated 

 within it by proteid metabolism, by the ammonia which it produces. 



