CH. XXXIX.] AMMONIA 589 



0'3 and 1/2 grammes; the average is 0*7 gramme. The ingestion of 

 ammonium carbonate does not increase the amount of ammonia in 

 the urine, but increases the amount of urea, into which substance the 

 ammonium carbonate is easily converted. But if a more stable salt, 

 such as ammonium chloride, is given, it appears as such in the urine. 



Under normal conditions the amount of ammonia depends on 

 the adjustment between the production of acid substances in met- 

 abolism and the supply of bases in the food. Ammonia formation is 

 the physiological remedy for deficiency of bases. 



When the production of acids is excessive (as in diabetes), or 

 when mineral acids are given by the mouth or injected into the 

 blood-stream, the result is an increase of the physiological remedy, 

 and excess of ammonia passes over into the urine. Under normal 

 circumstances ammonia is kept at a minimum, being finally converted 

 into the less toxic substance urea, which the kidneys easily excrete. 

 The defence of the organism against acids which are very toxic, is an 

 increase of ammonia formation, or, to put it more correctly, less of 

 the ammonia formed is converted into urea. 



Under the opposite conditions, namely, excess of alkali, either in 

 food or given as such, the ammonia disappears from the urine, all 

 being converted into urea. Hence the diminution of ammonia in the 

 urine of man on a vegetable diet, and its absence in the urine of 

 herbivorous animals. 



Not only is this the case, but if ammonium chloride is given to a 

 herbivorous animal such as a rabbit, the urinary ammonia is but little 

 increased. It reacts with sodium carbonate in the tissues, forming 

 ammonium carbonate (which is excreted as urea) and sodium chloride. 

 Herbivora also suffer much more from, and are more easily killed by, 

 acids than carnivora, their organisation not permitting a ready supply 

 of ammonia to neutralise excess of acids. 



Creatine and Creatinine. 



Creatine is an abundant constituent of muscle; its chemical 

 structure is very like that of arginine; it contains a urea radical, 

 and by boiling it with baryta it splits into urea and sarcosine 

 (methyl-glycine), as shown in the following equation : 

 C 4 H 9 N 3 2 + H,0 = CON 2 H 4 + C 3 H 7 NO 2 . 



[Creatine.] [Water.] [Urea.] [Sarcosine.] 



The same decomposition is shown graphically on p. 420. 



Creatine is absent from normal urine, but it is present in the 

 urine during starvation, in acute fevers, in women during involution 

 of the uterus, and in certain other conditions in which there is rapid 

 loss of muscular material. 



Its normal fate in the body is unknown ; it may be converted 

 into urea as in the foregoing equation, but injection of creatine into 



