CH. XXXVII.] AMMONIA 559 



urine. If the same occurs in tissue metabolism, we ought to find 

 considerable quantities of leucine, glycine, creatine, arginine, and 

 such substances in the blood, leaving the various tissues and entering 

 the liver ; but we do not. We do, however, constantly find ammonia, 

 which, after passing into the blood or lymph, has united with 

 carbonic acid to form either carbonate or carbamate of ammonium. 

 It is quite probable that the nitrogenous waste that leaves the 

 muscles and other tissues is split off from them as ammonia, and not 

 in the shape of large molecules of amino-acid, which are subsequently 

 converted into ammonia. The experiments outside the body which 

 most closely imitate those occurring within the body are those of 

 Drechsel, in which he passed strong alternating currents through 

 solutions of proteid-like materials. Such alternating currents are 

 certainly absent in the body, but their effect, which is a rapidly 

 changing series of small oxidations and reductions, are analogous to 

 metabolic processes ; under such circumstances the carbon atoms are 

 burnt off as carbon dioxide, and the nitrogen is split off in the form 

 of ammonia; by the union of these two substances ammonium 

 carbonate is formed. 



The following structural formulae exhibit the relationship between 

 ammonium carbonate, ammonium carbamate, and urea. The loss 

 of one molecule of water from ammonium carbonate produces 

 ammonium carbamate; the loss of a second molecule of water 

 produces urea 



/O.NH 4 /NH 2 /*H 2 



-\O.NH 4 -\O.NH 4 '\NJHj, 



[Ammonium carbonate.] [Ammonium carbamate.] [Urea or carbamide.] 



Ammonia. 



The urine of man and carnivora contains small quantities of 

 ammonium salts. In man the daily amount of ammonia excreted 

 varies between 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, like ammonium chloride, is given, it appears as 

 such in the urine. 



Under normal circumstances the amount of ammonia depends on 

 the adjustment between the production of acid substances in meta- 

 bolism 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, 



